Hebrews 6:13
"For when God made promise to Abraham, because he could swear by no greater, he sware by himself,"
Cross References (ranked by relevance)
The oath which he sware to our father Abraham,
But if ye will not hear these words, I swear by myself, saith the LORD, that this house shall become a desolation.
Thou wilt perform the truth to Jacob, and the mercy to Abraham, which thou hast sworn unto our fathers from the days of old.
I have sworn by myself, the word is gone out of my mouth in righteousness, and shall not return, That unto me every knee shall bow, every tongue shall swear.
For I have sworn by myself, saith the LORD, that Bozrah shall become a desolation, a reproach, a waste, and a curse; and all the cities thereof shall be perpetual wastes.
I will destroy also all the beasts thereof from beside the great waters; neither shall the foot of man trouble them any more, nor the hoofs of beasts trouble them.