What does Genesis 18:31 mean?
Abraham believes himself to be negotiating with the Lord, likely for the life of his nephew Lot and Lot's family. The Lord has revealed that He will investigate the sins of Sodom and Gomorrah and, by implication, bring judgment upon those cities. Lot lives in Sodom. This is not actually a bargaining process, however. God is playing the role of a patient parent, allowing a child to "talk out" a situation for their own benefit. Abraham is going to set the bar for righteousness in Sodom at a pathetically low level—and it still will not be enough. The purpose of this discussion is for our understanding; while God owes us no explanation, His conversation here gives us insight which proves His actions against Sodom to be entirely justified.Abraham started by asking if God would spare the city if He found 50 righteous people there. The Lord agreed. Then Abraham said, "What about 45?" The Lord agreed. Then 40. Then 30. Now Abraham asks for 20, while recognizing that he's being incredibly bold to speak this way to God. The Lord, again, agrees.