The protection of God is promised to Muhammad against all such as cut themselves off from him:—

If therefore they believe even as ye believe, then have they true guidance; but if they turn back then do they cut themselves off from you, and God will suffice to protect thee against them. Sura Al-Baqarah (ii) 131.

The accusation about hiding the testimony of the Scriptures to Muhammad is made in:—

Who is more in fault than he who concealeth the witness1 which he hath from God? Sura Al-Baqarah (ii) 134.

The next Sura in order is Sura Al-Baiyinah (xcviii) and here again the same charge is repeated:—

The unbelievers among the people of the Book and the polytheists did not waver until the clear evidence had come to them;
A messenger from God, reciting to them the pure pages wherein are true Scriptures.
Neither were they unto whom the Scriptures were given divided among themselves, till after this clear evidence had reached them. 1-3.2

[Continued from the previous page]
The commentator Husain says that the first wrath lies on those who reject Christ and the Gospels, and the other on those who reject Muhammad and the Qur'an. Vol.i, p.16.
خشمى بانكار عيسىا وانجيل وخشمى بانكار محمد وقران
Baidawi explains it as the punishment which follows on disbelief in Muhammad, and in Christ, or on their saying that 'Uzair (Ezra) was the Son of God. Vol. i, p. 72.
1 Baidawi says it means 'the concealing of the divine witness that Abraham was a Hanif, superior to a Jew or a Christian.'
شهادات الله لابراهيم بالحنقية والراعة عن اليهودية والنصرانية
Others say it refers to concealing witness about Muhammad. The charge is of hiding passages not of altering the text.
يبش از بعثت انحضرت همد مجتمع بودند بر تصديق وى وبعد ازانكة مبعوث شد مختلف شدند بعمى كرويدند بوى وبرخى كافر شدند
'Before the time of Muhammad, they all looked forward to the coming of a prophet whom they would follow, but when he came they wavered and were divided in opinion; some followed him, and some did not.' Tafsir-i-Husaini, vol. ii, p. 470.

The following verses continue the charge:—

And truly are there among them who torture the Scriptures with their tongues,1 in order that ye may suppose it to be from the Scripture, yet it is not from the Scripture; and they say, ' This is from God,' yet it is not from God; and they utter a lie against God, and they know they do so. Sura Al-'Imran (iii) 72.

In the latest Sura of all we have:—

They shift the words of Scripture from their places and have forgotten part of what they were taught. Sura Al-Ma'ida (v) 16.
O people of the Scriptures! Now is our Apostle come to you to clear up to you much that ye concealed of these Scriptures and to pass over many things. Now hath a light, and a clear Book come to you from God by which God will guide him who shall follow after His good pleasure to paths of peace, and will bring them out of the darkness to the light, by His will; and to the straight path will He guide them. Sura Al-Ma'ida (v) 18.1

The charge in all these verses is not that of altering the written text of the Scriptures, but of hiding

1 Baidawi's comment is, 'turn them in reading and divert them from the revealed words to the fabricated.'
يفتلونها على بقراءتة فيميلونة عن المنزل الى المحرفّ
Again there is no charge of altering the text.
2 The accusation here is that the Jews 'concealed passages in the Pentateuch concerning the praises of Muhammad and the verse of stoning, and that the Christians concealed the prophecy of Jesus given in the Injil concerning Ahmad.' The phrase 'much that ye concealed
مِمَّا كُنْتُمْ تُخْفُوْن is explained to mean what has just been stated concerning Jews and Christians.
ازانجة هستيد كة آن راينهان ميداريد من الكتب ازتوريت جون نعت محمد مصطفىا وآيت رجم واز انجيل جون بشارت عيسىا بة احمد
Tafsir-i-Husaini, vol. i, p. 140. Baidawi, vol. i. p. 251.