Hebrews 6:16-17 Men swear by someone greater then themselves: and an oath for confirmation to them puts an end to the problem.

NSB⁽ⁱ⁾ ¹⁶ Men swear by someone greater then themselves: and an oath for confirmation to them puts an end to the problem. ¹⁷ When God desired to show more convincingly to the heirs of the promise the unchangeable character of his purpose, he confirmed it with an oath.