Using more free and familiar carriage than became a brother and sister, but such as was allowable between husband and wife. See Deuteronomy 24:5 Proverbs 5:18,19. But that this was not the conjugal act, may easily be gathered from the circumstances of the time and place; which was open to Abimelech's view; and therefore that was not consistent either with Isaac's modesty or with his prudence, because he would not have her thought to be his wife.
Related Commentaries of Genesis 26:8
Genesis 26:8
8 And it came to pass, when he had been there a long time, that Abimelech king of the Philistines looked out at a window, and saw, and, behold, Isaac was sporting with Rebekah his wife.