Answering Islam - A Christian-Muslim dialog

Islamic Genetics

How a Jew’s testing of Muhammad proves that he was not a true prophet

Sam Shamoun and Jochen Katz

According to al-Bukhari, there was a Jew who went to see Muhammad when the latter first arrived to Medina in order to see whether he was a true prophet. The Jew, whom the tradition names as ‘Abdullah bin Salam, asked Muhammad specific questions to ascertain whether he was a true prophet or not.

Narrated Anas:
When 'Abdullah bin Salam heard the arrival of the Prophet at Medina, he came to him and said, "I am going to ask you about three things WHICH NOBODY KNOWS EXCEPT A PROPHET: What is the first portent of the Hour? What will be the first meal taken by the people of Paradise? Why does a child resemble its father, and why does it resemble ITS MATERNAL UNCLE?" Allah's Apostle said, "Gabriel has just now told me of their answers." 'Abdullah said, "He (i.e. Gabriel), from amongst all the angels, is the enemy of the Jews." Allah's Apostle said, "The first portent of the Hour will be a fire that will bring together the people from the east to the west; the first meal of the people of Paradise will be Extra-lobe (caudate lobe) of fish-liver. As for the resemblance of the child to its parents: If a man has sexual intercourse with his wife and gets discharge first, the child will resemble the father, and if the woman gets discharge first, the child will resemble her." On that 'Abdullah bin Salam said, "I testify that you are the Apostle of Allah." 'Abdullah bin Salam further said, "O Allah's Apostle! THE JEWS ARE LIARS, and if they should come to know about my conversion to Islam before you ask them (about me), they would tell a lie about me." The Jews came to Allah's Apostle and 'Abdullah went inside the house. Allah's Apostle asked (the Jews), "What kind of man is 'Abdullah bin Salam amongst you?" They replied, "He is the most learned person amongst us, and the best amongst us, and the son of the best amongst us." Allah's Apostle said, "What do you think if he embraces Islam (will you do as he does)?" The Jews said, "May Allah save him from it." Then 'Abdullah bin Salam came out in front of them saying, "I testify that None has the right to be worshipped but Allah and that Muhammad is the Apostle of Allah." Thereupon they said, "He is the evilest among us, and the son of the evilest amongst us," and continued talking badly of him. (Sahih al-Bukhari, Volume 4, Book 55, Number 546)

Ibn Kathir narrates a similar version from al-Bayhaqi:

“… He [ibn Salam] went to the Prophet and said, ‘I shall ask you three things for which ONLY a prophet would know the answers. They are… And what causes a child to resemble his father or his mother?’

“He replied, ‘Gabriel told me of these previously… And if the male’s liquid precedes that of the female, he will resemble the child, while if the FEMALE’S LIQUID precedes that of the male, she will resemble the child.’

“‘Abd Allah bin Salam exclaimed, ‘I testify that there is not god but God and that you are the Messenger of God; O Messenger of God, the Jews are a people of liars. If they learn about my accepting Islam before you ask them about me, they will lie to you.’” (Ibn Kathir, The Life of the Prophet Muhammad (Al-Sira al-Nabawiyya), translated by professor Trevor Le Gassick, reviewed by Dr. Ahmed Fareed [Garnet Publishing Limited, 8 Southern Court, south Street Reading RG1 4QS, UK; The Center for Muslim Contribution to Civilization: First paperback edition, 2000], Volume II, p. 195; comments within brackets as well as bold, capital and italic emphasis ours)

The above reports pose serious problems for the credibility of Muhammad as well as for the testimony of ibn Salam. These narratives contain both a major scientific blunder and a serious logical fallacy.

First, isn’t it somewhat ironic that ibn Salam is casting doubt on the truthfulness of Jews in general when himself was a Jew? Wouldn’t this severely undermine his own witness seeing that he too is a Jew? After all, if the Jews are liars then what does this make ibn Salam? What reason is there to exempt him from this judgment?

There is no evidence that the Jews are liars anymore than other people. Indeed there are liars among them, as there are also honest people, just as the Quran itself admits:

Among the people of the Scripture (Jews and Christians) is he who, if entrusted with a Cantar (a great amount of wealth, etc.), will readily pay it back; and among them there is he who, if entrusted with a single silver coin, will not repay it unless you constantly stand demanding, because they say: "There is no blame on us to betray and take the properties of the illiterates (Arabs)." But they tell a lie against Allah while they know it. S. 3:75 Hilali-Khan

Not all of them are alike; a party of the people of the Scripture stand for the right, they recite the Verses of Allah during the hours of the night, prostrating themselves in prayer. They believe in Allah and the Last Day; they enjoin Al-Ma'ruf (Islamic Monotheism, and following Prophet Muhammad) and forbid Al-Munkar (polytheism, disbelief and opposing Prophet Muhammad); and they hasten in (all) good works; and they are among the righteous. S. 3:113-114 Hilali-Khan

And there are, certainly, among the people of the Scripture (Jews and Christians), those who believe in Allah and in that which has been revealed to you, and in that which has been revealed to them, humbling themselves before Allah. They do not sell the Verses of Allah for a little price, for them is a reward with their Lord. Surely, Allah is Swift in account. S. 3:199 Hilali-Khan

Ibn Salam is simply slandering his own people and apparently trying to kiss up to Muhammad. He was smart and perhaps thought that in light of the way things were going the future of power in the region would probably lay with Muhammad, so he wanted to align himself with him. And he also knew that the Jews who were faithful to their Scriptures had no choice but to reject Muhammad, and would thus get themselves into trouble. Apparently ibn Salam wanted to be among the victors and therefore chose to defect to Muhammad’s side.

Second, and that is the fatal flaw in Ibn Salam’s “test”, if only a prophet would know the answers to the three questions which ibn Salam posed to Muhammad then how did the former know them? How did ibn Salam know that Muhammad answered correctly? Doesn’t this prove that ibn Salam must have also been a prophet? Again, notice the logic behind this:

  1. Nobody knows the answers to ibn Salam’s three questions except a prophet.
  2. Ibn Salam knew the answers to these questions.
  3. Therefore, ibn Salam must have been a prophet!

Either that, or Ibn Salam was not interested in a genuine test, merely in a pretext to switch sides. Or, the third alternative is that Ibn Salam was so blind that he did not see the logical problem with this alleged test, and thus he is not somebody we would trust to be able to distinguish a false prophet from a true one.

Even more importantly, Muhammad’s answer regarding why a child looks like his maternal uncle, i.e. his mother’s brother, was grossly mistaken. Notice the question and Muhammad’s reply:

Why does a child resemble its father, and why does it resemble ITS MATERNAL UNCLE?” Allah's Apostle said, “Gabriel has just now told me of their answers … As for the resemblance of the child to its parents: If a man has sexual intercourse with his wife and gets discharge first, the child will resemble the father, and if the woman gets discharge first, the child will resemble her.”

According to Muhammad Gabriel informed him that the child will look either like his father or maternal uncle depending on whoever discharges their liquid first, i.e. if the man happens to climax before the woman then the offspring will look like him but if the woman does so then the child will physically resemble her side of the family.

However, the sequence of discharge, i.e. whether the man or the woman climaxes first, has no influence on the future child. The statement of Muhammad actually contains several errors. First, the sperm of the man and the ovum of the woman are not fighting or racing against each other to see who is going to win the competition. On the contrary, they need to meet and unite and then the physical appearance of the child is determined by the combination of the characteristics of both. Usually children have characteristics of both sides, e.g. the form of the nose may resemble the father’s but the color of the eyes may be those of the mother, etc. It is not an either-or competition as asserted by Muhammad, but a combination of both elements, even if a child resembles one side of the family more closely than the other.

Second, Muhammad was talking about the observable discharge of the man and of the woman which his contemporaries were familiar with. And this is the worst error in Muhammad’s statement: The female discharge of fluid during intercourse has absolutely nothing to do with the genetical information that the child receives because the female discharge does not contain the ovum. The sexual fluids released by women during arousal and intercourse have the sole purpose of making intercourse enjoyable, but these fluids are released only in the vagina (where intercourse takes place). The ovum, on the other hand, can be fertilized only for a short period of time of about 12 to 24 hours after ovulation, and during this time it remains in the fallopian tubes. After that, the ovum disintegrates if it was not fertilized there. In other words, if not fertilized in the fallopian tubes the ovum is already dead when it reaches the uterus, let alone the vagina where the observable sexual fluids are. The sexual fluids of the man and the woman meet and mix in the vagina but the ovum is not there. Moreover, only the sperm can penetrate the cervix to move towards the ovum in the fallopian tubes. The rest of the sexual fluids of both man and woman remain in the vagina. In particular, the sexual fluids of the woman don’t play a role anymore where sperm and ovum meet and when the characteristics of the new child are decided, i.e. when sperm and ovum unite their chromosomes.

Third, recognizing that the sexual fluids of the woman have simply nothing to do with the genetic information of the child conceived through intercourse, some Muslims may try to argue that the discharge of the woman refers to her ovulation. However, that won’t work either. While Muhammad’s statement, "If a man has sexual intercourse with his wife and gets discharge first, the child will resemble the father, and if the woman gets discharge first, the child will resemble her", even sounds as if every intercourse results in a child (which is obviously wrong), it is clear that he speaks about the sexual discharge that happens DURING intercourse. However, the ovum is usually not released during intercourse. Even if a couple would have sex every day, ovulation is a short burst once a month and not triggered by sexual arousal so that it is extremely unlikely to happen exactly during intercourse. Due to the slow speed of the ovum and the sperm and the short window of time in which an ovum can be fertilized, fertilization of an ovum usually happens with sperm from sexual intercourse that has taken place a couple of days before ovulation. The way Muhammad speaks about this process is simply not in agreement with medical reality.

Some Muslims even want to understand this hadith as talking about gender determination instead of resemblance. Even though the formulation of the question in this hadith, particularly the version found in Sahih al-Bukhari, does not allow such an interpretation, it would add another interesting error. The reason is that if intercourse (ejaculation, male discharge) happens (shortly) after ovulation (female discharge) then the probability for a boy to be conceived is much higher than for a girl – exactly the opposite of Muhammad’s assertion. The reason is that on average X-chromosome carrying sperm cells move slower but live longer, while Y-chromosome carrying sperm cells move faster. Thus, if the ovum is already available, the Y-chromosome carrying sperm has a higher probability to reach the ovum first – assuming there was no intercourse for about a week before ovulation, so that X-chromosome carrying sperm from previous intercourse has already died. (For details see many webpages on gender determination for babies based on the methodology of Landrum B. Shettles – for example: 1, 2, 3.)1

In any case, medical science tells us that this is a statistical issue of higher and lower probabilities. After all, there are usually more than a 100 million sperm cells involved. Muhammad on the other hand formulated an explanation of certainty which is another aspect of his ignorant pronouncement.

In conclusion, whatever way one looks at it, this statement is a scientific error which Muhammad attributed to Gabriel, which in turn means that Allah is the source of Muhammad’s gross scientific blunder and mistaken notion of genetics.

This basically leaves us with the following options. Either ibn Salam was dishonest because he knew the logical fallacy in his claims and therefore was aware that what he presented was not a genuine test of a prophet. Hence, the whole incident was nothing more than a pretext for him to switch sides.

Or ibn Salam believed this was a genuine and valid test. If so, then the above observations disqualify him from making such a judgment because only a prophet can know the answers. And since ibn Salam wasn’t a prophet he wasn’t in any position to determine whether Muhammad was right or wrong.

However, Muhammad’s replies showed that he failed this test in actually two ways. First, he gave the wrong scientific answer. Second, as a true prophet he should have exposed the fatal flaw in the test, i.e. he should have pointed out that since nobody can know if his (or anyone’s) answer is correct without being a prophet himself, the test is useless. Now, THAT response would have been impressive.

But it gets even worse. According to these reports, Muhammad received this blatantly wrong “scientific information” the same way he received portions of the Quran – from Gabriel!  However, since this information is clearly wrong, this either implies that neither Allah nor Gabriel know a thing about genetics, or Muhammad simply lied since he wasn’t receiving any information from Gabriel. This further destroys all confidence in the other “revelations” that Muhammad claims to have received from the same source.

What all of this suggests is that either ibn Salam was simply duping Muhammad into believing his lies which the latter fell for hook, line and sinker! This in turn proves that Muhammad was a false prophet and that the real Gabriel never spoke to him.

Or it actually demonstrates that Muhammad simply parroted the mistaken scientific understanding and folklore of that time. Muhammad simply promoted the same ignorant and mistaken views concerning science and other issues which his contemporaries believed and which he tried to pass off as revelations from God. In so doing Muhammad made God the author of these myths and scientific blunders.

However, since we are today in a position of knowing the truth about genetics, Muhammad’s mistaken answer proves beyond any reasonable doubt that he was a false prophet.



1 However, the issue of how long the ovum can be fertilized, how long sperm is alive, and how fast they can move under which circumstances, and the consequences this has for "natural" gender selection is still a matter of some debate and current research. Anyway, for the discussion of this hadith, this is relatively irrelevant since the hadith is about resemblance not gender, and about the female discharge of sexual fluids which has nothing to do with the ovum.

Answering Islam Home Page