Don’t you think that Bible teachers are doing a terrible job? It took quite a while for anyone in this thread to point out that there was no Bible of any sort at the time of Abraham. It seems to me that most believers seem to get their knowledge from Biblical highlights from sermons and bible story books.
This is not irrelevant. It is telling that even after Moses no one mentions the law until around the time of Jeremiah - which is strong support for the Bible actually being written much later than claimed.
As to your point, from where do you think morality comes? Abraham got a direct command from God. What would the justification be for his refusing it? Why do you suppose he should have thought he could outsmart god? Even if he saw a contradiction, why do you suppose God would be bound by such things?
This is the portion read during Yom Kippur, the holiest day of the year, and the meaning I was taught was very clear - obeying in the expectation that God will make things work out.