Jesus is summarizing material from lots of different Old Testament passages, including Leviticus 19:12, Numbers 30:2, Deuteronomy 23:21–23, and Ecclesiastes 5:4–5. 1 The third commandment (Exodus 20:7) is specifically in view since oaths, by definition, called on a deity to bear witness to them. False oaths were a misuse of God’s name. 2
33 “Again you have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn.’