Ramban on Genesis 19:5

Their intention was to prevent people from traveling through their territory...because they thought that since the land is beautiful, like a heavenly garden, many will come (to live there) and they despised charity. Lot, however, was wealthy, so they accepted him when he came to them and requested residence among them, and perhaps they received him out of honor to Abraham...According to our sages they [the people of Sodom] had every bad quality, but their judgment was sealed on this sin because they did not strengthen the hand of the poor and downtrodden, and they were consistent in this sin more than others. As well, every other nation in the world extends kindness to neighbors and to the poor, so, [in contrast,] there was not among all the peoples any that compared to Sodom in cruelty... Know that the judgment of Sodom is an expression of the greatness of the Land of Israel; since Israel is the inheritance of God, it does not suffer men of hateful deeds (anshei toevot from the Hebrew word toevah, abomination). Since the land [in the future after Israel settles it] will completely throw out people because of their abominations, it already vomited out this nation because they were more evil than any other, both to heaven and to people. [Translation by Rabbi Steven Greenberg]