How can one respond to the insinuation that the Prophet Muhammad (peace be upon him) was influenced by and received knowledge from rabbis and monks?

This is an old and recurring شبهة (specious argument). They accused him, peace and blessings be upon him, of taking from a Roman man, so Allah revealed: "And We certainly know that they say, 'It is only a human being who teaches him.' The tongue of the one they allude to is foreign, and this is a clear Arabic tongue."

This specious argument does not stand on sound ground for several reasons: 1. He, peace and blessings be upon him, was unlettered; he could not read or write. Thus, there is no justification for accusing him of taking from the People of the Book through their scriptures. 2. His enemies from Quraysh acknowledged that the revelation descended upon him was the most eloquent speech and unlike human speech. 3. The Qur'an exposed the distortions and falsehoods of previous scriptures. Had he been influenced by them, this would not have happened. 4. It has not been historically proven that he met with Jewish rabbis or Christian monks before the revelation descended upon him to learn from them.