As Greg recently pointed out, Abram/Abraham is not the great moral leader you would expect from the founder of God’s great nation. He gives up his wife to Pharaoh in Gen. 12, is treated well as a result, but eventually God intervenes and Abram leaves with his wife, life, and wealth intact. He does it again in chapter 20, this time to the king of Gerar, Abimelek.
There are three lessons from these stories I remember being taught as a child. Abram/Abraham should have had faith enough in God to protect him from Pharaoh and Abimelek that he needn’t lie. A half-truth is still a lie, which is a sin. Despite this sin, God kept his promise to Abraham and Sarah, that through them he would make a nation.
There is no doubt that intentionally deceiving someone is wrong, but the lesson here comes from the moral authority of two humans. Pharaoh (Gen. 12:18-19) and Abimelek (Gen. 20:9-10), not God, question Abram/Abraham about his deception, implying that his actions were wrong. God, if anything, only reinforces Abram/Abraham’s poor behavior. Because God intervenes so dramatically, Abram/Abraham leaves with greater wealth given by Pharaoh (Gen. 12:16,20) and Abimelek (Gen. 20:14-16).
I suppose there is a fourth lesson here: a great nation needs great wealth.