Neither shalt thou swear by thy head, because thou canst not make one hair white or black.
Perjury is impiety toward God and injustice toward man combined; it renders a man obnoxious to divine wrath. The ancients understood this so well they turned their swearing formulas into curses upon themselves, wishing God's judgment if they lied. This shows how deeply nations have always felt that God must curse the false swearer, if He be God.
AI summary
Commenting on Matthew 5:33-37
Neither shalt thou swear by thy head,.... This also was a common form of swearing among the Jews: take a few instances. "If anyone is bound to his friend by an oath, and says to him, vow unto me , "by the life of thy head"; R.
Verse 36. Thy head. This was a common oath. The Gentiles also many of them used this oath. To swear by the head was the same as to swear by the life; or to say, I will forfeit my life if what I say is not true. God is the Author of the life, and to swear by that, therefore, is the same as to swear by him.