Hebrews 6:15 YLT

¹³  For to Abraham God, having made promise, seeing He was able to swear by no greater, did swear by Himself,

¹⁴  saying, 'Blessing indeed I will bless thee, and multiplying I will multiply thee;'

¹⁵  and so, having patiently endured, he did obtain the promise;

¹⁶  for men indeed do swear by the greater, and an end of all controversy to them for confirmation 'is' the oath,

¹⁷  in which God, more abundantly willing to shew to the heirs of the promise the immutability of his counsel, did interpose by an oath,