What does Genesis 19:13 mean?

Finally, the two angels disguised as humans reveal their full mission to Lot and his family. They have been sent by the Lord, who intends to destroy Sodom (Genesis 19:24–25). Later verses credit the action to God, while the angels here use the expression "we" when referring to Sodom's impending ruin. This might refer to the combined actions of God and His messengers, much the same way a player on a team might say "we will…" when discussing an activity. Or, it might mean that God's destruction will be accomplished through the agency of these same angels. Either way, their role is to move forward God's plans for Sodom's judgment.

With this statement, the outcry against Sodom's people has reached the Lord, in every conceivable sense. The time of judgment has come. The angels will give Lot one last chance to grab any relatives or friends and take them with him. God's justice against Sodom will be satisfied, but in His mercy these angels will rescue all who are with Lot, Abraham's nephew.