Matthew Poole and continuators on Genesis 20:4

4 But Abimelech had not come near her : and he said, LORD, wilt thou slay also a righteous nation ?

(i. e.) Had not yet lyen with her. A modest expression like that of knowing a woman, Gen. 4. 1. or going in to her, Gen. 6. 4. or touching her, Prov. 6. 29. 1 Cor. 7. 1. by which we are taught to use modesty in our speeches, and not, with the rude Cynicks, to express all things by their proper names. This clause and history was necessary to be added here for Sarahs vindication, and especially for the demonstration of Isaacs original from Abraham and Sarah, according to Gods promise.

(i. e.) Innocent as to this matter, compare 2 Sam. 4. 11.

For he knew it was just and usual for God to punish a Nation for their Kings sins, and therefore, as became a good Prince, he is solicitous and prays for the safety of his nation: Or else by Nation he may mean his Family, for some of them were not involved in the guilt of this fact.