'Oath' in the Bible

For men swear by the greater: and in every dispute of theirs the oath is final for confirmation.

Wherein God, being minded to show more abundantly unto the heirs of the promise the immutability of his counsel, interposed with an oath;

And inasmuch as it is not without the taking of an oath

(for they indeed have been made priests without an oath; but he with an oath by him that saith of him, The Lord sware and will not repent himself, Thou art a priest for ever);

For the law appointeth men high priests, having infirmity; but the word of the oath, which was after the law, appointeth a Son, perfected for evermore.