A hard lesson on intercessory Prayer

Read Genesis 18.

This is the sixth recorded time the LORD has directly revealed Himself to Abraham.  Each occurrence provided direction, a promise, or affirmation concerning God's covenant with him.

In the previous chapter, the LORD promised that a son named Isaac would indeed be Abraham's heir.  Here, the LORD appeared again to announce that the child would be born within the next year.  What humanly was impossible for this elderly couple presented no problem for God.
"Is anything too hard for the LORD?" (v.14)

The first half of the chapter appears to be almost incidental to the real mission.  The two angels, appearing as human men were on their way to deal with the sin of Sodom and Gomorrah.  Notice that the two angels appeared as men, not with glowing auras, and not with wings.  This is consistent with all other appearances of angels in the scriptures.  

The LORD, then, asked this question: "Shall I hide from Abraham what I am about to do?" (v.17)  God's patience with the cities in the valley had run out.  Judgment against their wickedness would come swiftly and totally.

When he realized this would affect Lot, Abraham began to intercede on his behalf.  Finally, Abraham's request is reduced to a number equal to that of Lot, his children and their spouses.  Sadly, only three escaped alive.

Was God allowing Abraham to negotiate the souls of these people?  No.  God already knew what He was going to do.  But Abraham did not.  One result of earnest prayer is surrendering our wills to what God wants done in the area of our requests.  Then, we must trust Him fully for the outcome.  Our belief in prayer is not based upon getting our way but in the One who is worthy of our trust.