This passage is always confusing for me. I don’t really understand the correlation between the three men in Genesis 18 and God. It says the Lord appeared and then the three men, so it seems that these three men were separate from the Lord. I think that this is just a form that the Lord took to speak to Abraham. Maybe this is similar to the other times God has talked to Abraham, but it just never told us how God did it before. I imagine that this has to be something similar to the Angel of the Lord, except in the form of three men. Although the passage says that it is the Lord speaking, I think we are led to believe that the Lord is speaking through these three men.
Apparently Abraham did not mistake them for any one else, as evident by his generosity. I have heard it said that this was just basic common courtesy in this time period, but I find it hard to believe that Abraham, who had hundreds of servants, would single out a random group of men walking down the road. There must have been something about them or maybe there was just something about Abraham that let him recognize God. They were truly in the form of men since they ate the food.
Abraham then starts to taking a very noble, yet annoying attitude. I do admire his love for his fellow man, but I feel like he could have gotten to the bottom line a little faster. Do you really have to go down in increments of ten or can you just ask what is the minimum?