I do not know of which chapter and verse the rabbi spoke, but this is one that may at least be similar to it:
God is not man, that he should lie, or a son of man, that he should repent. Has he said, and will he not do it? Or has he spoken, and will he not fulfil it? (Numbers 23:19).
At the time this was written, it was absolutely correct that God was not a man: the Incarnation had not yet occurred; the Son of God was still pure spirit only, as the Father and the Holy Spirit always have been pure spirit before and after the Incarnation. And, in this verse, the emphasis is that God does not share man’s faults and imperfections.
What must be proven for the rabbi’s rejection of the Incarnation to be correct is that God never became man. Christianity holds that God the Son chose to enter human history and become man at a later point in time than the Old Testament was written. That assertion does not contradict this passage. Unless this verse is the one the rabbi mentioned, I cannot comment on the rabbi’s verse without a citation.