The Hebrew of Genesis 18:20 says only that the outcry of Sedom and Amorah is great and their sin very heavy. Targum Pseudo-Jonathan will not leave that vague. It hands us, in Aramaic, the specific crime.
"The cry of Sedom and Amorah," God tells the ministering angels, is because "they oppress the poor, and decree that whosoever giveth a morsel to the needy shall be burned with fire."
Read that again. Sodom did not merely neglect the poor. It legislated against kindness. The city passed a civic ordinance making charity itself a capital offense. A single crust of bread handed to a hungry stranger could get you burned alive. The most famous midrashic elaboration of this law is the story of Lot's daughter Paltit, who secretly fed a starving man and was executed for it when Sodom found out.
This is why the destruction is framed in the Targum as precisely proportional. They burned the generous. They will be burned by fire from heaven (Genesis 19:24). Middah k'neged middah — measure for measure — is Jewish theology's signature, and nowhere sharper than here.
The takeaway: a society's character is measured not by how it treats those who give but by how it treats those who receive. Criminalize compassion, and the heavens stop pretending not to notice.