What sawest thou that thou hast done this thing? By this question the king provides against the future. He thinks that Abraham had not practiced this dissimulation inconsiderately; and, since God was grievously offended, he fears to fall again into the same danger. He therefore testifies, by an inquiry so earnest, that he wishes to remedy the evil. Now, it is no common sign of a just and meek disposition in Abimelech, that he allows Abraham a free defense. We know how sharply, and fiercely, they expostulate, who think themselves aggrieved: so much the greater praise, then, was due to the moderation of this king, towards an unknown foreigner. Meanwhile, let us learn, by his example, whenever we expostulate with our brethren, who may have done us any wrong, to permit them freely to answer us.

And Abimelech said unto Abraham,.... Continuing his discourse with him:
what sawest thou, that thou hast done this thing? he desires to know what he had observed, either in him or his people, that gave him any reason to conclude that they were a lustful people, and would stick at nothing to gratify their lusts, which put him upon taking such a method to secure his life, lest they should kill him for his wife's sake.

"What sawest thou," i.e., what hadst thou in thine eye, with thine act (thy false statement)? Abimelech did this publicly in the presence of his servants, partly for his own justification in the sight of his dependents, and partly to put Abraham to shame. The latter had but two weak excuses: (1) that he supposed there was no fear of God at all in the land, and trembled for his life because of his wife; and (2) that when he left his father's house, he had arranged with his wife that in every foreign place she was to call herself his sister, as she really was his half-sister. On the subject of his emigration, he expressed himself indefinitely and with reserve, accommodating himself to the polytheistic standpoint of the Philistine king: "when God (or the gods, Elohim) caused me to wander," i.e., led me to commence an unsettled life in a foreign land; and saying nothing about Jehovah, and the object of his wandering as revealed by Him.

What sawest thou that thou hast done this thing - What reason hadst thou to think, that if we had known her to be thy wife, thou wouldst have been exposed to any danger by it?