Genesis 26:10
And Abimelech said, What is this thou hast done unto us? one of the people might lightly have lien with thy wife, and thou shouldest have brought guiltiness upon us. And Abimelech said, What is this thou hast done unto us? one of the people might lightly have lien with thy wife, and thou shouldest have brought guiltiness upon us.
Genesis 26:10 belongs to Isaac's sojourn in the land of the Philistines after famine carried him there, a sojourn marked by abundant blessing in that land and by differences with the Philistines, and the chapter closes with Esau's marriages. It stands as part of the renewal to Isaac of the covenant to Abraham's seed that the land and its blessings would belong to Abraham's descendants, a promise later confirmed to Jacob and Israel. It stands within God's speaking to Isaac in Genesis 26:2-15 by an audible voice, showing how after sin entered the world God no longer met with man face to face as before sin but instructed His people by an audible voice among various ways of speaking in different periods. It belongs to the account of God's special providence over Isaac as one of the progenitors of the promised Seed, showing how God worked for him and blessed him in consequence when he refused to contend for his rights and was willing to yield more than justice and commit his cause to God. It is part of Isaac's experience in Philistia in which his faithful, public life led the local ruler and his advisers to recognize that the Lord was with him and that he was blessed by the Lord.
The verse is Abimelech's stern rebuke of Isaac for concealing that Rebekah was his wife and presenting her as his sister. He warned that his deception put the people at risk because one of the people might lightly have taken or slept with her as a wife, unknowingly. One of them might unknowingly have taken Rebekah as his wife, bringing guilt upon the community and making his people accountable.
The verse shows that Abimelech, king of Gerar, knew that lying with or taking another man's wife was sin, a great sin, and that such an act would have brought guiltiness and sin and blame upon himself and his people and kingdom and made the community accountable. This guilt would have followed even though the act would have been unknowing, because Isaac had said Rebekah was his sister and Abimelech and his people believed it. The verse proves that the law against adultery, the seventh commandment, was known and binding long before Sinai and was understood by mankind in general.