The Jews know that the Prophet is True, but they hide the Truth
Allah states that the scholars of the People of the Scripture know the truth of what Allah's Messenger was sent with, just as one of them knows his own child, which is a parable that the Arabs use to describe what is very apparent. Similarly, in a Hadith, Allah's Messenger said to a man who had a youngster with him:
؟ قَالَ: نَعَمْ يَا رَسُولَ اللهِ أَشْهَدُ بِهِ
(Is this your son) He said, "Yes, O Messenger of Allah! I testify to this fact.'' Allah's Messenger said:
(Well, you would not transgress against him nor would he transgress against you.)
According to Al-Qurtubi, it was narrated that `Umar said to `Abdullah bin Salam (an Israelite scholar who became a Muslim), "Do you recognize Muhammad as you recognize your own son'' He replied, "Yes, and even more. The Honest One descended from heaven on the Honest One on the earth with his (i.e., Muhammad's) description and I recognized him, although I do not know anything about his mother's story.''
Allah states next that although they had knowledge and certainty in the Prophet, they still:
(conceal the truth.)
The Ayah indicates that they hide the truth from the people, about the Prophet, that they find in their Books,
(while they know it. ) Allah then strengthens the resolve of His Prophet and the believers and affirms that what the Prophet came with is the truth without doubt, saying:
((This is) the truth from your Lord. So be you not one of those who doubt.)
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, "You cannot convince by argument those who are disputing with you about the wisdom of the change of the giblah because they are not disposed to listen to any reasoning on account of their deep prejudices and obduracy: nor can you end this dispute by adopting the giblah of anyone of them; for all of them have different qiblahs, and, as a Prophet of Allah, you cannot make compromises on the principle of "give and take". Therefore the only thing you have to do is to stick to Our Commandments strictly and firmly. If you turn away from these, you will be transgressing the limits of Prophethood and showing ingratitude towards the favour of leadership with which We have blessed you."
This Arabic idiom is employed when one knows something with certainty and has absolutely no doubt about its identity. The metaphor has been derived from the fact that none can make any mistake in recognizing one's own children. Here it has been used to show that the learned people of the Jews and Christians knew it as a fact that the Ka'bah was built by the Prophet Abraham, just as they knew their own children. They also knew that the Holy Temple at Jerusalem was built by the Prophet Solomon some 1,300 years after the Ka'bah was built by the Prophet Abraham. The Ka'bah, therefore, had priority and superiority over the "Temple" and the Jews and the Christians should have no difficulty in recognizing and acknowledging it as the qiblah in the light of the above historical facts.
The truth comes from your Lord; then be not among the doubters. i.e. 'after the suns of certainty have appeared to you do not yield to the results of mere guessing'. The address is to [the Prophet] but what is intended by it is the community.