Hebrews 6:16-19

For men verily swear by the greater: and an oath for confirmation is to them an end of all strife. Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath: that by two immutable things, in which it was impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us: which hope we have as an anchor of the soul, both sure and stedfast, and which entereth into that within the veil