9 Then Abimelech called in Abraham and said, "What have you done to us? What have I ever done to you that you would bring on me and my kingdom this huge offense? What you've done to me ought never to have been done." 10 Abimelech went on to Abraham, "Whatever were you thinking of when you did this thing?" 11 Abraham said, "I just assumed that there was no fear of God in this place and that they'd kill me to get my wife. 12 Besides, the truth is that she is my half sister; she's my father's daughter but not my mother's. 13 When God sent me out as a wanderer from my father's home, I told her, 'Do me a favor; wherever we go, tell people that I'm your brother.'"
Matthew Henry's Commentary on Genesis 20:9-13
Commentary on Genesis 20:9-13
(Read Genesis 20:9-13)
See here much to blame, even in the father of the faithful. Mark his distrust of God, his undue care about life, his intent to deceive. He also threw temptation in the way of others, caused affliction to them, exposed himself and Sarah to just rebukes, and yet attempted an excuse. These things are written for our warning, not for us to imitate. Even Abraham hath not whereof to glory. He cannot be justified by his works, but must be indebted for justification, to that righteousness which is upon all and unto all them that believe. We must not condemn all as hypocrites who fall into sin, if they do not continue in it. But let the unhumbled and impenitent take heed that they do not sin on, thinking that grace may abound. Abimelech, being warned of God, takes the warning; and being truly afraid of sin and its consequences, he rose early to pursue the directions given him.