Genesis 20:11-13

"And Abraham said, Because I thought, surely the fear of God is not in this place; and they will slay me for my wife's sake. And moreover she is indeed my sister, the daughter of my father, but not the daughter of my mother; and she became my wife: 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."

Abraham here offered a three-fold excuse:

1. He feared for his safety that men might kill him for the sake of his wife. Note that this was the object of the device at the time it was initiated. Abraham did not here allege that to have been the root of his fear in this instance.
   
2. He had not actually told a falsehood, since Sarah was indeed his half-sister. Still it was a lie, spoken with intent to deceive.
   
3. It was a habit of long standing, doubtless practiced over and over again throughout many years, and the indication in this is that Abraham was merely pleading that, "I, or we, always do this when we are traveling in strange territory." Inherent in such an admission is that Abraham had totally failed to learn the lesson he should have learned on that other occasion in Egypt when such a habit had involved him in serious trouble.
   

Speculation as to why Abraham had not offered a similar defense of his actions in the presence of Pharaoh, with accompanying allegations of "some other source" attempting to present Abraham in a little better light, are pointless in the light of Pharaoh's commanding Abraham to be removed from his kingdom in the same breath with the inquiry as to why Abraham had lied to him, thus giving no opportunity to reply. The issue was already settled, as was not the case here.