“Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths:”
King James Version (KJV)
5:33 Our Lord here refers to the promise made to the pure in heart of seeing God in all things, and points out a false doctrine of the scribes, which arose from their not thus seeing God. What he forbids is, the swearing at all, by any creature, in our ordinary conversation: both of which the scribes and Pharisees taught to be perfectly innocent. #Exod 20:7|.
Mt 5:33 Thou shalt not forswear thyself. See Le 19:12 Nu 25:2. The Jews held that this only prohibited swearing falsely and by the name of God.