As you read chapter eighteen, note that God himself appears to Abraham. He is part of the group. We know that because of the proper name for God given in verse ten. Did Abraham recognnize the Lord immediately? We are not sure, but something led him to believe these visitors were not ordinary. By the end of the story, it is evident Abraham knows who his visitors are.
At first we are arrested by Abraham’s wealth, respect, and hospitality, all seen in the meal Abraham prepares and serves. The flour alone would have been enough to make forty one pound loaves – entirely more than the three visitors would need – not to mention the “tender calf” also served on the menu. These visitors are men of the highest importance; so important that Abraham provides this feast of a meal and serves them as their servant, not deigning to eat with them, but waiting on them from the side. Once we know that he knows God is present, it serves to underscore the respect he had for the Lord.
But then there is this conversation God has with himself: “Shall I hide from Abraham what I am about to do?” Abraham will become the father of a great nation. As their patriarch, Abraham needs to know how the Lord thinks and works that he might pass it on to his descendants. And so, in revealing his plan for Sodom, we see something of the nature of God.
God cares how people act – even those who are not His own. He has no covenant with the people of Sodom and Gomorrah, but He finds their behavior repulsive and intends to hold them accountable for it. If he does this for the uninitiated, how much more for those who know Him (or are supposed to know Him)? But God is gracious. He will allow someone to intercede for the wicked and is willing to delay suspend their punishment because of the righteous. God is a listener. He is open to Abraham’s thoughts, open to considering other views, and willing to adjust His own behavior so as not to offend those He loves.
This Genesis description of God is instructive for us, for it helps us to understand the goodness and severity of God – precisely what God wanted Abraham to know.