John Calvin Commentary Genesis 20:10

"And Abimelech said unto Abraham, What sawest thou, that thou hast done this thing?" — Genesis 20:10 (ASV)

What sawest thou that thou hast done this thing? By this question, the king guards against the future. He thinks that Abraham had not practiced this deception thoughtlessly; and, since God was severely offended, he fears falling into the same danger again. Therefore, by such an earnest inquiry, he testifies that he wishes to remedy the evil.

Now, it is a significant sign of a just and meek disposition in Abimelech that he allows Abraham a free defense. We know how sharply and fiercely those who think themselves wronged protest; therefore, all the more praise was due to the moderation of this king toward an unknown foreigner. Meanwhile, let us learn from his example: whenever we reason with our brothers and sisters who may have wronged us, to allow them to answer us freely.