The Angel of God that is mentioned in Judges 13:6 is the same Angel that had appeared to Moses, Joshua, and others, and was none other than Christ. The Old Testament reveals that Jesus Christ made several bodily appearances before He was born in the flesh. Here are some references:
1-In Gen. 18, it says how Jesus, along with two of His angels, visited Abraham. Starting in Gen. 18:13, He is called “the LORD.” Whenever the word LORD appears in scripture with all caps, this identifies God’s name Jehovah or Yahweh. As this chapter ends, two of the men begin a journey to Sodom while Jesus remains behind to tell Abraham that Sodom will be destroyed. Upon learning of Sodom’s upcoming destruction, Abraham intercedes on their behalf with Jesus.
2-In Gen. 32:24-30, it says how Jacob wrestled with a Being. This Being was Jesus Christ. Since Jacob held his own against Jesus in the wrestling match, he was granted a blessing. His name was changed to Israel. Israel means “he who prevails with God” or “he will rule as God (rules).” Jacob had literally prevailed with God by wrestling with Him in the person of Jesus. Jacob realized who he wrestled with in Gen. 32:30 by naming the place Peniel, meaning “the face of God,” knowing he had seen Him and lived.
3-In Judges 6:11-24, the soon-to-be judge Gideon is greeted by the Angel of the Lord. The Angel of the Lord sat down under an oak tree. Gideon asks why the Lord had not fulfilled the wonders God promised the people of Israel. The reaction was that “the LORD turned to him” and replied, which identifies the Angel as the Lord Himself. Gideon later brought food that the Angel of the Lord’s staff consumed with fire, followed by a dramatic disappearance. Gideon’s reply to such a sight in verse 22 was, “Ah, Sovereign LORD! I have seen the angel of the LORD face to face!” He feared dying from seeing the living God. Absent in form but still clearly present, the Lord replies in voice in verse 23, “Peace! Do not be afraid. You are not going to die.” Clearly, this angel was no angel at all, but the Lord God Himself!
4-In Genesis 16-7-13, Hagar, calls the Angel of the Lord “LORD,” “God,” and “One.”
5-In Exodus 3:2-6, the Angel of the LORD declares Himself to be God from the burning bush to Moses with the use of the title “I Am.” Jesus claimed that title for Himself in John 8:58. Jesus by saying He was “I Am” was the great Yahweh, also known to us today as Jehovah God.
6-In Josh. 5:13-15, it speaks of how Christ appeared to Joshua who was near Jericho when he saw a man with a sword drawn. Immediately Joshua wanted to know if he was friend or foe and he was told by the man that he was Captain of the Lord’s host. Upon hearing this, Joshua fell on his face and worshiped Him. This man did not stop Joshua from worshiping Him as any other servant of the Lord would do (Acts 10:26; 14:15; Rev. 19:10; 22:9 where servants of God stopped other men from worshiping them). Joshua asked Jesus what His message was and Jesus responded by telling Joshua to take off his shoes because he was on holy ground, which is the same thing He told Moses in Exodus when He appeared to him in a burning bush.
7-The prophet Hosea also refers to the Lord both as God and as Angel (Hosea 12:3, 4).
In His service,