Matthew 5:35

“Nor by the earth, for it is his footstool, etc.] That the Jews were wont to swear by the earth, is clear from the above mentioned instances; and is condemned by Christ for this reason, because the earth is God’s “footstool”, referring, as before, to (<236601>Isaiah 66:1) on which he treads; and where he also manifests forth his glory, and is a considerable part of the work of his hands. Neither by Jerusalem, which the Jews used to swear by: such forms of vows as these are to be met with in their writings f330; “as the altar, as the temple, µlçwryk, “as Jerusalem”;” that is, by Jerusalem, I vow I will do this, or the other thing. “R. Judah says, he that says Jerusalem (i.e. as Bartenora…”

“Nor by the earth; for it is his footstool--(quoting Isa 66:1); neither by Jerusalem for it is the city of the great King--(quoting Psa 48:2).”

“But I say unto you, Swear not at all - That is, in the manner which he proceeds to specify. Swear not in any of the common and profane ways customary at that time. By heaven; for it is God’s throne - To swear by that was, if it meant anything, to swear by Him that sitteth thereon, Matthew 23:22. Nor by the earth; for it is his footstool - Swearing by that, therefore, is really swearing by God. Or perhaps it means: 1.That we have no right to pledge, or swear by, what belongs to God; and, 2.That oaths by inanimate objects are unmeaningful and wicked. If they are real oaths, they are by a living Being, who has power to take vengeance. A footstool is that on which the feet rest when sitting. The…”

“the earth: Psa 99:5 the city: Ch2 6:6; Psa 48:2, Psa 87:2; Mal 1:14; Rev 21:2, Rev 21:10 Matthew 5:36”