'Oath' in the Bible

Indeed men swear [an oath] by one greater than themselves, and with them [in all disputes] the oath serves as confirmation [of what has been said] and is an end of the dispute.

In the same way God, in His desire to show to the heirs of the promise the unchangeable nature of His purpose, intervened and guaranteed it with an oath,

so that by two unchangeable things [His promise and His oath] in which it is impossible for God to lie, we who have fled [to Him] for refuge would have strong encouragement and indwelling strength to hold tightly to the hope set before us.

And indeed it was not without the taking of an oath [that Christ was made priest]

(for those Levites who formerly became priests [received their office] without [its being confirmed by the taking of] an oath, but this One [was designated] with an oath through the One who said to Him,“The Lord has swornAnd will not change His mind or regret it,‘You (Christ) are a Priest forever’”).

For the Law appoints men as high priests who are weak [frail, sinful, dying men], but the word of the oath [of God], which came after [the institution of] the Law, permanently appoints [as priest] a Son who has been made perfect forever.