Matthew 5:33

33 `Again, ye heard that it was said to the ancients: Thou shalt not swear falsely, but thou shalt pay to the Lord thine oaths;

Matthew 5:33 In-Context

31 `And it was said, That whoever may put away his wife, let him give to her a writing of divorce;
32 but I -- I say to you, that whoever may put away his wife, save for the matter of whoredom, doth make her to commit adultery; and whoever may marry her who hath been put away doth commit adultery.
33 `Again, ye heard that it was said to the ancients: Thou shalt not swear falsely, but thou shalt pay to the Lord thine oaths;
34 but I -- I say to you, not to swear at all; neither by the heaven, because it is the throne of God,
35 nor by the earth, because it is His footstool, nor by Jerusalem, because it is a city of a great king,
Young's Literal Translation is in the public domain.