'Faithlessly' in the Bible

Do we not all have one Father? Has not one God created us? Why do we deal treacherously with one another, profaning the covenant of our fathers [with God]?

“For I hate divorce,” says the Lord, the God of Israel, “and him who covers his garment with wrong and violence,” says the Lord of hosts. “Therefore keep watch on your spirit, so that you do not deal treacherously [with your wife].”