Genesis chapters 18-19 is a powerful proof text for these reasons:
First, is clearly shows Yahweh walking around on the earth in human form with two angels.
They are called "three men". Yahweh and the two angels are called men, because they appeared as men.
Second: God taking human appearance on earth is called a "Theophanies". There are several other examples of Theophanies in scripture.
Few of those examples can be found in Genesis 3:8-10; Genesis 18-19; Genesis 26:2,24; Exodus 3:2; Exodus 6:3; Leviticus 16:2; 1 Samuel 3:21; Judges 13:15-23; 2 Chronicles 3:1
Third, you have Genesis 19:24 that has two distinct Yahweh's: One on earth and one in heaven. "Then Yahweh [on earth in human form] rained on Sodom and Gomorrah brimstone and fire from Yahweh [in spirit form in heaven] out of heaven. Genesis 19:24.
In this story, Abraham meets God (Jesus) and the two angels. Jesus came right out and said He was the one who talked to Abraham. This is what Jesus meant when He said, "Your father Abraham rejoiced to see My day, and he saw it and was glad." (John 8:56) God appearing to Abraham is an example of a Theophanies.
Elijah is also said to have seen Jesus in heaven in Isa 6 + John 12:41. Jesus appearing to Elijah is not be an example of a "Theophanies" because Jesus was seen in heaven.
Amazingly, Amos 4:10-11 has two Yahweh's just like Gen 19:24 when talking about the exact same event!: "Yet you have not returned to Me, [Father]" declares Yahweh [Father]. "I [Father] overthrew you, as God [Son] overthrew Sodom and Gomorrah, And you were like a firebrand snatched from a blaze; Yet you have not returned to Me [Father]" declares Yahweh [Father]." (Amos 4:10-11)
Commentary and corresponding texts in block quotes for clear understanding
Three men: Yahweh + 2 angels appear to Abraham
"Now the Lord appeared to him by the oaks of Mamre, while he was sitting at the tent door in the heat of the day. When Abraham lifted up his eyes and looked, behold, three men were standing opposite him; and when he saw them, he ran from the tent door to meet them and bowed himself to the earth" Genesis 18:1-2
It was God who was standing before Abraham in human form.
"And Yahweh said to Abraham, "Why did Sarah laugh, saying, 'Shall I indeed bear a child, when I am so old?' " Genesis 18:13
Three men intend on visiting Sodom.
"Then the [three] men rose up from there, and looked down toward Sodom; and Abraham was walking with them to send them off. Yahweh said, "Shall I hide from Abraham what I am about to do, " Genesis 18:16-17
God, in human form says this directly to Abraham
"Yahweh said, "Shall I hide from Abraham what I am about to do" Genesis 18:17
God, in human form says this directly to Abraham. This verse shows that Yahweh would go personally to Sodom and see for Himself.
"And Yahweh said, "The outcry of Sodom and Gomorrah is indeed great, and their sin is exceedingly grave. I [Yahweh] will go down now, and see if they have done entirely according to its outcry, which has come to Me; and if not, I will know." Genesis 18:20
The two angels, called men, depart, leaving Yahweh behind to talk to Abraham.
"Then the men turned away from there and went toward Sodom, while Abraham was still standing before Yahweh. " Genesis 18:22
Abraham replies to the man and calls him Lord. Notice the Lord (the man) intended on destroying it.
"Then he said, "Oh may the Lord [adonai] not be angry, and I shall speak only this once; suppose ten are found there?" And He said, "I will not destroy it on account of the ten." " Genesis 18:32
Yahweh, in human form, left Abraham and went to Sodom to join the two angels who left earlier.
"As soon as He had finished speaking to Abraham, Yahweh departed, and Abraham returned to his place." Genesis 18:33
Two angels visit Lot. During this time, these two are never called Yahweh, neither are they addressed by Lot as Yahweh.
"Now the two angels came to Sodom in the evening as Lot was sitting in the gate of Sodom. When Lot saw them, he rose to meet them and bowed down with his face to the ground. " Genesis 19:1
Lot addresses these two angels, as Adonai, not Yahweh.
And he said, "Now behold, my lords, please turn aside into your servant's house"" Genesis 19:2
Notice the angels say that Yahweh sent them. Yahweh is not present with Lot the way he was with Abraham. The change is powerful proof of our major premise.
"for we are about to destroy this place, because their outcry has become so great before Yahweh that Yahweh has sent us to destroy it." " Genesis 19:13
Yahweh, the man who was talking to Abraham, was to destroy Sodom.
"Lot went out and spoke to his sons-in-law, who were to marry his daughters, and said, "Up, get out of this place, for Yahweh will destroy the city."" Genesis 19:14
Again the two are called angels, never Yahweh.
"When morning dawned, the angels urged Lot, saying, "Up, take your wife and your two daughters who are here, or you will be swept away in the punishment of the city." " Genesis 19:15
There are two Yahweh's present in this verse and the context. The man talking to Abraham, called Yahweh, was standing on the earth and commanded the city destroyed. Yahweh in heaven then sent the fire out of heaven.
"Then Yahweh [on earth in human form] rained on Sodom and Gomorrah brimstone and fire from Yahweh [in spirit form in heaven] out of heaven." Genesis 19:24