Genesis 20:13

And it came to pass, when God caused me to wander from my father's house, that I said unto her, This is thy kindness which thou shalt show unto me: at every place whither we shall come say of me, He is my brother. This was an explanation, an attempted defense, but a questionable excuse at best, that he had not supposed that men feared God in the land of Abimelech, that consequently he feared for his life on account of Sarah, that he had made an agreement with his wife to have her masquerade as his sister. The Lord could very well have protected him and his wife without such questionable means. The Bible does not hide from us the weaknesses and foibles of the saints, but frankly tells them for our warning. If we are honestly engaged in the work of our calling, we need not resort to subterfuges to save our lives. Without the will of God not a hair of our heads may be touched.