Genesis 20:7

Now therefore restore the man [his] wife,.... Which will be a full proof and evidence to all of the integrity of thy heart, and the innocence of thine hands, which thou pleadest, and which I own:

for he [is] a prophet; familiar with God, dear unto him, a friend of his, to whom he communicates his secrets; is able to foretell things to come, as well as to interpret the mind of God, and instruct in the knowledge of divine things, all which agrees with Abraham's character; and he is the first man that is dignified in Scripture with the title of a prophet; so he is called in the Apocrypha:

"Beware of all whoredom, my son, and chiefly take a wife of the seed of thy fathers, and take not a strange woman to wife, which is not of thy father's tribe: for we are the children of the prophets, Noe, Abraham, Isaac, and Jacob: remember, my son, that our fathers from the beginning, even that they all married wives of their own kindred, and were blessed in their children, and their seed shall inherit the land.'' (Tobit 4:12)

Jarchi thinks this is observed to encourage Abimelech to return his wife to him, because being a prophet he knew he had not touched her, and therefore would receive her more readily, and entertain no ill opinion of her; but rather it is mentioned for the reason following:

and he shall pray for thee, and thou shalt live; it being one part of the business of a prophet to pray for others, and make intercession for them, especially in any distress or trouble, see Jeremiah 27:18. Prophets were praying persons, had usually a great gift in prayer, and great power with God, and prevailed with him for the good of others; and such an one was Abraham; and it is here intimated, that upon the restoration of his wife to him, as he was familiar with God, and had an interest with him, he would make use of it, and pray for Abimelech, that whatsoever offence he had been guilty of to God or men, it might be forgiven, and that he might be healed of the disease with which he was smitten, and so recover of it, and live in health and happiness:

and if thou restore [her] not, know thou, that thou shalt surely die,

thou, and all that [are] thine: if he proceeded to take her to be his wife, and defile her, he is strongly assured that he should die, death being the punishment for adultery before the law of Moses, see

Genesis 38:24; and not only he, but all his family, especially such who had been, or would be accessory to this affair, and even all who might he justly punished of God for other sins they had committed; and Abimelech being punished, both in his own person, and in his servants and subjects, the greater his punishment was, the greater abhorrence and detestation was shown to the sin he would be guilty of, to deter him from which this threatening is given out.