Even as Sodom and Gomorrah, and the cities about them in like manner, giving themselves over to fornication, and going after unnatural lust, are set forth for an example, suffering the vengeance of eternal fire.
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Aquinas Study Bible
AD 2017
The unnatural lust in which the Sodomites indulged was homosexuality, which is wrong because it cannot lead to procreation. (Oecumenius) So by conflagration of the people of Sodom he gives the example of those who exchange the grace of our Lord for self-indulgence. (St. Bede)