Genesis 26:7

She is my sister. As Abraham had declared his wife to be his sister (Genesis 12:11, 12; 20:2, 11), so also did Isaac; but the manner in which God protected Rebekah was very different from that in which Sarah was preserved. No one so much as touched her. This experience and one other (Genesis 25:28) are the only recorded instances in the life of Isaac of deviation from strict rectitude. Ashamed of his own conduct, Abraham may not have warned Isaac by a narration of his own failures in this respect. More likely, however, Abraham had told Isaac but, as so often happens, Isaac had to learn the lesson for himself through bitter experience. How often the sins of parents are perpetuated in their children! But hereditary weaknesses never free the children from personal accountability for their own mistakes (see Ezekiel 18:20).