Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King.
All Commentaries on Matthew 5:35 Go To Matthew 5
Theophylact of Ochrid
AD 1107
Since the Jews had heard God say, "Heaven is My throne, and earth is My footstool" (Is. 66:1) they would swear by such things. In prohibiting them from swearing by these things, the Lord does not say, "Do not swear by them because heaven is good and great, and earth is useful." Instead He says, "Do not swear by them because the one is the throne of God and the other is His footstool," so that idolatry would not occur. For they might make gods out of those elements by which they swore, which indeed had happened before.
