Genesis 22:16

22:16 and said, “‘I solemnly swear by my own name,’ decrees the Lord, ‘that because you have done this and have not withheld your son, your only son,

Genesis 26:3-4

26:3 Stay in this land. Then I will be with you and will bless you, for I will give all these lands to you and to your descendants, and I will fulfill the solemn promise I made to your father Abraham. 26:4 I will multiply your descendants so they will be as numerous as the stars in the sky, and I will give them all these lands. All the nations of the earth will pronounce blessings on one another using the name of your descendants.

Hebrews 6:13

6:13 Now when God made his promise to Abraham, since he could swear by no one greater, he swore by himself,