Deuteronomy 24:4
Her first husband, who had sent her away, may not take her back after she has been wife to another; for that is disgusting to the Lord: and you are not to be a cause of sin in the land which the Lord your God is giving you for your heritage.
Jeremiah 3:1
They say, If a man puts away his wife and she goes from him and becomes another man's, will he go back to her again? will not that land have been made unclean? but though you have been acting like a loose woman with a number of lovers, will you now come back to me? says the Lord.
Leviticus 18:24-28
Do not make yourself unclean in any of these ways; for so have those nations whom I am driving out from before you made themselves unclean:
Joshua 22:17-18
Was not the sin of Baal-peor great enough, from which we are not clear even to this day, though punishment came on the people of the Lord,