When God assures Abraham of his blessings because of Abraham’s obedience to him, God swears by himself. Genesis 22:16 starts as follows “And (the Lord) said, By myself have I sworn (promised or vowed)” What does this signify? Hebrews 6:13 gives the answer to this. It reads “For when God made promise to Abraham, because he could swear by no greater, he sware by himself,” This phrase signifies not only the greatness of God, but establishes the fact that there is no one greater.

Points to ponder:
Our God is a great God and he does wondrous things (Psalm 86:10) and in blessing you and me, if he had to swear by someone, he would have to swear by himself, for there is no on greater than him.

Genesis 22:16 (KJV)
16 And said, By myself have I sworn, saith the Lord, for because thou hast done this thing, and hast not withheld thy son, thine only son:

Hebrews 6:13-17 (KJV)
13 For when God made promise to Abraham, because he could swear by no greater, he sware by himself,
14 Saying, Surely blessing I will bless thee, and multiplying I will multiply thee.
15 And so, after he had patiently endured, he obtained the promise.
16 For men verily swear by the greater: and an oath for confirmation is to them an end of all strife.
17 Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath:

Psalm 86:10 (KJV)
10 For thou art great, and doest wondrous things: thou art God alone.