Looking up, he saw three figures standing near him. Perceiving this, he ran from the entrance of the tent to greet them and, bowing to the ground, he said, “My lords! If it please you, do not go on past your servant.
Genesis 18:2-3 (The Contemporary Torah, JPS 2006)
Most translations say “my Lord” in this verse (singular), but this is actually the plural noun “adonai.”
The rabbis debate over whether this is intended as a majestic title (like “Elohim”), or if Abraham is calling all three of them “lords”.
But “you” is singular here.
Let a little water be brought; bathe your feet and recline under the tree.
Genesis 18:4 (The Contemporary Torah, JPS 2006)
But in the next verse, the verbs switch back to referring to a plural subject. "Bathe" and "recline" are plural verbs here.
Grammatically, it is very strange. One possibility is that Abraham is sometimes just talking to one of the men, and sometimes talking to all three.
Scholars debate this. It’s quite odd.