Sometimes Genesis 18:1-3 is used in an attempt to prove the trinity. These texts say, “And the Lord appeared unto him in the plains of Mamre: and he sat in the tent door in the heat of the day; And he lift up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground, And said, My Lord, if now I have found favour in thy sight, pass not away, I pray thee, from thy servant.” Some people claim that the “three men” who appeared unto Abraham were the supposed three members of the trinity.
However, there are some serious problems with this claim. First of all, it is impossible for any of these three individuals to be God, the Father, for the Bible says, “No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him” (John 1:18). The Bible says that the Father dwells “in the light which no man can approach unto; whom no man hath seen, nor can see” (1 Timothy 6:16). God told Moses, “Thou canst not see my face: for there shall no man see me, and live” (Exodus 33:20). Several prophets in the Bible saw at least faint representations of the Father in vision, but no sinful man has ever been able to actually look at the Father and live to tell the story. Because of this we can be absolutely certain that God, the Father, was not one of the “three men” who appeared to Abraham.
So, who appeared to Abraham? The Bible says that “the Lord appeared unto him.” Whenever the King James Version of the Bible uses the word Lord with all capital letters it signifies that the Hebrew name of God, Yahweh, was written in the original text. Yahweh appeared unto Moses. As we have already seen, the person referred to here is not God, the Father, demonstrating that there is someone else who uses this name.
God told Moses, “Behold, I send an Angel before thee, to keep thee in the way, and to bring thee into the place which I have prepared. Beware of him, and obey his voice, provoke him not; for he will not pardon your transgressions: for my name is in him” (Exodus 23:20, 21). Here, God told Moses that an Angel would go before the children of Israel. This was no literal angel. God said, “my name is in him.” Paul informed us that the “spiritual Rock that followed them… was Christ” (1 Corinthians 10:4).
We are also told that Jesus is “so much better than the angels, as he hath by inheritance obtained a more excellent name than they” (Hebrews 1:4). Jesus Christ received a name from His Father by inheritance. This must be a name that His Father also has, and this name is Yahweh. Jesus Christ used this name in Genesis 18, and it was He who appeared to Abraham, not as a trinity, but as one single individual, and there were two literal angels with Him. The Bible says, “And the men turned their faces from thence, and went toward Sodom: but Abraham stood yet before the Lord” (Genesis 18:22). Two of the three went toward Sodom, and only one stayed behind to talk with Abraham. There is only one Person referred to as “the Lord” in this verse, and He is the Son of God. We know that only two of the men went toward Sodom and that they were angels, for when they arrived, the Bible says, “And there came two angels to Sodom” (Genesis 19:1).
Genesis 18 definitely does not prove or even hint at the idea that God is a trinity of three persons in one God. The Son of God and two angels is not a trinity.