Who was the angel that Jacob wrestled with at Jabbok?
"Then Jacob was left alone; and a Man wrestled with him until the breaking of day. Now when He saw that He did not prevail against him, He touched the socket of his hip; and the socket of Jacob's hip was out of joint as He wrestled with him. And He said, "Let Me go, for the day breaks." But he said, "I will not let You go unless You bless me!" So He said to him, "What is your name?" He said, "Jacob." And He said, "Your name shall no longer be called Jacob, but Israel; for you have struggled with God and with men, and have prevailed." Then Jacob asked, saying, "Tell me Your name, I pray." And He said, "Why is it that you ask about My name?" And He blessed him there. And Jacob called the name of the place Peniel: "For I have seen God face to face, and my life is preserved."" (Genesis 32:24-30).
As you can see, though asked for a name, the person declined to give one. Jacob concluded that the man he wrestled was God because he knew about his past and because he damaged his hip joint with just a touch. A passage in Hosea gives us further clues: "He took his brother by the heel in the womb, and in his strength he struggled with God. Yes, he struggled with the Angel and prevailed; he wept, and sought favor from Him. he found Him in Bethel, and there He spoke to us - that is, the LORD God of hosts. The LORD is His memorable name" (Hosea 12:3-5). Notice the parallel points: Jacob struggled with God, but he struggled with the Angel. One explanation for the parallel is that "angel" means a messenger. Thus as a representative of God, Jacob wrestled with God's representative and therefore he wrestled with God.
However, in the Genesis account, Jacob sought a blessing from the man and wanted to know the man's name. He received the blessing, but not the name. Hosea said that Jacob received the blessing, but found the name of his benefactor in Bethel. There it was revealed that the blessing came from the Lord God of hosts (Yahweh). "Then God appeared to Jacob again, when he came from Padan Aram, and blessed him. And God said to him, "Your name is Jacob; your name shall not be called Jacob anymore, but Israel shall be your name." So He called his name Israel. Also God said to him: "I am God Almighty. Be fruitful and multiply; a nation and a company of nations shall proceed from you, and kings shall come from your body. The land which I gave Abraham and Isaac I give to you; and to your descendants after you I give this land." Then God went up from him in the place where He talked with him. So Jacob set up a pillar in the place where He talked with him, a pillar of stone; and he poured a drink offering on it, and he poured oil on it. And Jacob called the name of the place where God spoke with him, Bethel" (Genesis 35:9-15).
In another instance, Manoah (Samson's father) asked the Angel of the Lord the same question and received a similar answer. "And the Angel of the LORD said to Manoah, "Though you detain Me, I will not eat your food. But if you offer a burnt offering, you must offer it to the LORD." (For Manoah did not know He was the Angel of the LORD.) Then Manoah said to the Angel of the LORD, "What is Your name, that when Your words come to pass we may honor You?" And the Angel of the LORD said to him, "Why do you ask My name, seeing it is wonderful?"" (Judges 13:16-18).
Agur expressed how little he knew in Proverbs 30: "Surely I am more stupid than any man, and do not have the understanding of a man. I neither learned wisdom nor have knowledge of the Holy One. Who has ascended into heaven, or descended? Who has gathered the wind in His fists? Who has bound the waters in a garment? Who has established all the ends of the earth? What is His name, and what is His Son's name, If you know?" (Proverbs 30:2-4). Take note that the Old Testament hinted of God the Father and God the Son; neither of whom mankind truly knows their names.
Because of all these parallels, many scholars believe that Jacob wrestled with the being known as "the Angel of the Lord." It is possible that this is God the Son who interacted with men in the form of an angel. Rather than get into a detailed discussion of who the Angel of the Lord is in this reply, let me refer you to the sermon: "Exploring the Nature of God in the Old Testament" and read through the fourth section which deals with the Angel of the Lord.