At Genesis 22:1, "Now it came about after these things that "GOD" tested Abraham. At verse 2, "And He/God said, "Take now your son, your only son, whom you love Isaac, and go to the land of Moriah; and offer him there as a burnt offering on one of the mountains of which I will tell you."
Verse 9, Then they came to the place of which God had told him; and Abraham built the altar there, and arranged the wood, and bound his son Isaac, and laid him on the altar on top of the wood." Verse 10, "And Abraham stretched out his hand and took the knife to slay his son."
Verse 11, "But the angel of the Lord called to him from heaven, and said, "Abraham, Abraham!" And he said, "Here I am. Verse 12, "And he said/the angel of the Lord, "Do not stretch out your hand against the lad, and do nothing to him; for now I know that you fear God, since you have not withheld your son, your only son, from Me." At verses 13-14 the Lord provides a ram for Abraham to sacrifice.
Verse 15, "Then the angel of the Lord called to Abraham a second time from heaven, vs16, and said, (the angel of the Lord is speaking), By Myself I have sworn, declares the Lord, because you have done this thing, and have not withheld your son, your only son, vs17, "indeed I will greatly multiply your seed as the stars of the heavens, and as the sand which is on the seashore; and your seed shall possess the gate of their enemies."
Verse 18, "And in your seed all the nations of the earth shall be blessed, because you have obeyed MY VOICE." The following is a list of verses where God Himself calls out from heaven. Genesis 21:17, Exodus 20:22, Deuteronomy 4:36, Nehemiah 9:13, Daniel 4:31 and other in the Old Testament.
Here are some in the New Testament. Mark 1:11, Luke 3:22, John 12:28, 2 Peter 1:18, Revelation 14:2 and Revelation 12:10. There are also others in the NT. Since God had no problem speaking from heaven numerous times, why does the angel of the Lord call out to Abraham from heaven two times at Genesis 22:11, and at Genesis 22:15 claiming to be God?
This is confirmed by the writer of the book of Hebrews at Hebrews 6:13-14, "For when God made the promise to Abraham, since He could swear by no one greater, HE SWORE BY HIMSELF, vs14, saying, I will surely bless you, and I will surely multiply you."