"God is not a man, that He should lie, Nor a son of man, that He should repent; Has He said, and will He not do it? Or has He promised, and will He not make it good?"
This single passage presents 4 challenges to Christian beliefs:
1) God clearly says that He is not a man.
2) God is clear that He will not turn around on His word which means if He did become a man it would make Him a hypocrite.
2) God says that men are liars, repenters who are clearly beneath Him. This again shows God has zero intention of becoming a man.
4) This contradicts other Old Testament verses which Christians use to prove God is a man or will become one.