'Deal Treacherously' in the Bible

Have we not all one father? has not one God created us? why do we deal treacherously every man against his brother, by profaning the covenant of our fathers?

And did not he make them one? Yet had he the remnant of the spirit. And why one? That he might seek a godly offspring. Therefore take heed to your spirit, and let none deal treacherously against the wife of his youth.