Adam Clarke on Genesis 26:10

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.