Abraham saw three...

[18:1] And the LORD appeared to him by the oaks of Mamre, as he sat at the door of his tent in the heat of the day. [2] He lifted up his eyes and looked, and behold, three men were standing in front of him. When he saw them, he ran from the tent door to meet them and bowed himself to the earth [3] and said, “O Lord, if I have found favor in your sight, do not pass by your servant. [4] Let a little water be brought, and wash your feet, and rest yourselves under the tree, [5] while I bring a morsel of bread, that you may refresh yourselves, and after that you may pass on—since you have come to your servant.” So they said, “Do as you have said.” [6] And Abraham went quickly into the tent to Sarah and said, “Quick! Three seahs of fine flour! Knead it, and make cakes.” [7] And Abraham ran to the herd and took a calf, tender and good, and gave it to a young man, who prepared it quickly. [8] Then he took curds and milk and the calf that he had prepared, and set it before them. And he stood by them under the tree while they ate. (Genesis 18:1-8 ESV)


Sure sounds like God was speaking with Abraham. The three were obviously important to Abraham, he bowed down to them, he called one of them Lord, he washed their feet, and he served them his best food and watched while they ate.  Later in the story we see these verses, [17] The LORD said, “Shall I hide from Abraham what I am about to do, [18] seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him? (Genesis 18:17-18 ESV) Here the Lord is referencing what he is about to do for him, and that all nations will be blessed in him. Was He referencing His work to come at the cross as Messiah again, and that all who believe in Him will be saved? Then, in the New Testament we find this verse, [56] Your father Abraham rejoiced that he would see my day. He saw it and was glad.” [57] So the Jews said to him, “You are not yet fifty years old, and have you seen Abraham?” [58] Jesus said to them, “Truly, truly, I say to you, before Abraham was, I am.” [59] So they picked up stones to throw at him, but Jesus hid himself and went out of the temple. (John 8:56-59 ESV).


We don't find any references as to who two of the three were that visited Abraham, but One of the three that visited and then spoke to him, was God the Son, Jesus. Jesus said that Abraham saw Him, and was glad, and rejoiced to see Him.