Isaac had now laid aside all thoughts of going to Egypt, and, in obedience to the heavenly vision, sets up his staff in Gerar, the country in which he was born (Gen 26:6), yet there he enters into temptation, the same temptation that his good father had been once and again surprised and overcome by, namely, to deny his wife, and to give out that she was his sister. Observe,
I. How he sinned, Gen 26:7. Because his wife was handsome, he fancied the Philistines would find some way or other to take him off, that some of them might marry her; and therefore she must pass for his sister. It is an unaccountable thing that both these great and good men should be guilty of so strange a piece of dissimulation, by which they so much exposed both their own and their wives' reputation. But we see, 1. That very good men have sometimes been guilty of very great faults and follies. Let those therefore that stand take heed lest they fall, and those that have fallen not despair of being helped up again. 2. That there is an aptness in us to imitate even the weaknesses and infirmities of those we have a value for. We have need therefore to keep our foot, lest, while we aim to tread in the steps of good men, we sometimes tread in their by-steps.
II. How he was detected, and the cheat discovered, by the king himself. Abimelech (not the same that was in Abraham's days, ch. 20, for this was nearly 100 years after that, but this was the common name of the Philistine kings, as Caesar of the Roman emperors) saw Isaac more familiar and pleasant with Rebekah than he knew he would be with his sister (Gen 26:8): he saw him sporting with her, or laughing; it is the same word with that from which Isaac has his name. He was rejoicing with the wife of his youth, Pro 5:18. It becomes those in that relation to be pleasant with one another, as those that are pleased with one another. Nowhere may a man more allow himself to be innocently merry than with his own wife and children. Abimelech charged him with the fraud (Gen 26:9), showed him how frivolous his excuse was and what might have been the bad consequences of it (Gen 26:10), and then, to convince him how groundless and unjust his jealousy of them was, took him and his family under his particular protection, forbidding any injury to be done to him or his wife upon pain of death, Gen 26:11. Note, 1. A lying tongue is but for a moment. Truth is the daughter of time; and, in time, it will out. 2. One sin is often the inlet to many, and therefore the beginnings of sin ought to be avoided. 3. The sins of professors shame them before those that are without. 4. God can make those that are incensed against his people, though there may be some colour of cause for it, to know that it is at their peril if they do them any hurt. See Psa 105:14, Psa 105:15.

Thou shouldest have brought guiltiness upon us - It is likely that Abimelech might have had some knowledge of God's intentions concerning the family of Abraham, and that it must be kept free from all impure and alien mixtures; and that consequently, had he or any of his people taken Rebekah, the Divine judgment might have fallen upon the land. Abimelech was a good and holy man; and he appears to have considered adultery as a grievous and destructive crime.

And Abimelech charged all his people,.... All his subjects throughout his kingdom, and particularly the inhabitants of Gerar, and more especially his courtiers and servants about him:

saying, he that toucheth this man or his wife; that does any injury to one either by words or deeds, or behaves immodestly to the other, or attempts to ravish her; this being sometimes used as a modest expression carnal knowledge of a woman; or that does either of them any harm or hurt in any respect whatever:

shall surely be put to death; this severe edict he published, in order to deter his subjects from using them ill, to which they might be provoked by Isaac's dissimulation, and by his evil suspicions of them.