How can you explain Numbers 23:19 -- "God is not a man, that he should lie, nor a son of man, that he should change his mind"? Wouldn't that disprove the concept of the Trinity?
No, because the Trinity is not three people! The Holy Trinity is a three-in-one, or triune, God.
The point of the passage is that although he is personal, God does not share in our human fallibility. It has nothing to say about the incarnation or the trinitarian nature of deity.