Are you then hopeful that they will believe for your sake? And indeed a party from among them heard the word of Allah, then after understanding it, they altered it, and they know (this).
Allah (SWT) is giving a hint to Muslims that the Jews will not believe just for their sake. Some of them had heard the word of Allah (SWT) in the form of Torah, Zuboor and the Injeel and understood it. They knew from these sources about Prophet Muhammed (PBH) but they altered this information. Some of the Jews might have told the Muslims that they believed in the Prophethood of Muhammed (PBH) because it was written in their books. This might have prompted other Jews to object, because they felt that Muslims would argue with them on the day of resurrection before Allah (SWT) that even after having information about Prophet Muhammed (PBH) they did not accept him as the last messenger of Allah and the Quran revealed to him as the final message of Allah (SWT). Therefore Allah (SWT) is informing them that whether they hide or proclaim He knows everything.