God appears to Avraham as he sits at the opening to his tent. He looks up and he sees three men. He runs to meet them and says, “My Lord, please do not go away from your servant. Let me get some water and wash your feet and rest under the tree.”
The simple meaning of this is that God appears to Avraham in the shape of three men who he sees and invites in. When he says, “My Lord, please do not go away,” he is addressing the leader. And later it transpires they are messengers from another world. From this we might learn that angels are really humans acting in such a way as to actualize some Divine plan. We can all be agents of God in some way or another. Avraham clearly saw them as humans, because he offers them creature comforts.
But the Midrash puts a very different spin on this narrative. The Midrash sees the following sequence. God appears to Avraham and they are communicating spiritually, when Avraham looks up and sees three men. He turns to God and says, “My Lord, please do not go away.” And then he turns to the three men and says, “Let me get some water,” etc.
The idea here is that, however important God is, there are certain types of human crises or obligations that are so important that one can actually tell God to wait. Important as God is, as spirituality is, in the end it must enhance our relationship with other humans. This world we are in is predominantly a human one. This must determine our priorities. Of course, if we do not have a spiritual base to our lives to begin with, we might be inclined to a more selfish outlook. But in the end, being a good person is what God really wants of us.