For when God made a promise to Abraham, because He could swear by no one greater, He swore by Himself,
Hebrews 6:13
Surrounding context
6:12 that you do not become sluggish, but imitate those who through faith and patience inherit the promises.
6:13 For when God made a promise to Abraham, because He could swear by no one greater, He swore by Himself,
6:14 saying, "Surely blessing I will bless you, and multiplying I will multiply you."