'Took an Oath' in the Bible

Then they came to urge David to eat bread while it was still day, but David took an oath: “May God punish me and do so severely if I taste bread or anything else before sunset!”

Then Solomon took an oath by the Lord: “May God punish me and do so severely if Adonijah has not made this request at the cost of his life.

They took an oath to the Lord in a loud voice, with shouting, with trumpets, and with rams’ horns.