The sin of Sodom
The sin of Sodom — inhospitality and violence (with Ezekiel 16:49) or same-sex acts; the dispute runs through Leviticus 18:22 and 20:13, Romans 1, 1 Corinthians 6:9 and 1 Timothy 1:10 across traditions.
Genesis 19:1-11
1The two angels came to Sodom at evening. Lot sat in the gate of Sodom. Lot saw them, and rose up to meet them. He bowed himself with his face to the earth,
2and he said, “See now, my lords, please come into your servant’s house, stay all night, wash your feet, and you can rise up early, and go on your way.” They said, “No, but we will stay in the street all night.”
3He urged them greatly, and they came in with him, and entered into his house. He made them a feast, and baked unleavened bread, and they ate.
4But before they lay down, the men of the city, the men of Sodom, surrounded the house, both young and old, all the people from every quarter.
5They called to Lot, and said to him, “Where are the men who came in to you this night? Bring them out to us, that we may have sex with them.”
6Lot went out to them through the door, and shut the door after himself.
7He said, “Please, my brothers, don’t act so wickedly.
8See now, I have two virgin daughters. Please let me bring them out to you, and you may do to them what seems good to you. Only don’t do anything to these men, because they have come under the shadow of my roof.”
9They said, “Stand back!” Then they said, “This one fellow came in to live as a foreigner, and he appoints himself a judge. Now we will deal worse with you than with them!” They pressed hard on the man Lot, and came near to break the door.
10But the men reached out their hand, and brought Lot into the house to them, and shut the door.
11They struck the men who were at the door of the house with blindness, both small and great, so that they wearied themselves to find the door.
Romans 1:26-27
26For this reason, God gave them up to vile passions. For their women changed the natural function into that which is against nature.
27Likewise also the men, leaving the natural function of the woman, burned in their lust toward one another, men doing what is inappropriate with men, and receiving in themselves the due penalty of their error.
What each tradition says
Rabbinic / Midrashic
Jacobs and Ochser report that in Sodom anyone who gave bread and water to the poor was condemned to death by fire. They recount two girls, one poor and one rich, at a well: the poor girl gave the rich girl her water and received bread; when this became known, both were burned alive.
Joseph Jacobs and Schulim Ochser (1901-1906), The Jewish Encyclopedia, vol. 11, s.v. 'Sodom' (New York: Funk & Wagnalls) — section 'In Rabbinical Literature'
Patristic
Augustine holds that offenses contrary to nature are always and everywhere to be detested and punished. The Sodomites committed such offenses; if all nations did so, all would be guilty under divine law, because God did not make people to abuse one another in that way. Such lust violates the fellowship between God and us by polluting His created nature.
Augustine of Hippo (354-430), The Confessions of St. Augustin (trans. J. G. Pilkington), in Nicene and Post-Nicene Fathers, ser. 1, vol. 1 (New York: Christian Literature Publishing Co., 1886) — Book III, ch. 8, §15 (on offences contrary to nature, 'such were those of the Sodomites')
Catholic
Thomas Aquinas states that the unnatural vice is a species of lust. It occurs by procuring pollution without copulation for venereal pleasure, called uncleanness or effeminacy; by copulation with an undue species, called bestiality; or by copulation with an undue sex, male with male or female with female, as the Apostle states in Romans 1:27, called the vice of sodomy.
Thomas Aquinas (1225-1274); trans. Fathers of the English Dominican Province, Summa Theologica, Secunda Secundae (II-II), q. 154, 'On the Parts of Lust' (New York: Benziger Bros., 1947) — q. 154, art. 11, 'Whether the unnatural vice is a species of lust?', body of the article
Orthodox
Chrysostom states that all these affections were vile, but chiefly the mad lust after males, since the soul suffers and is more dishonored in sins than the body in diseases. He adds that here too he deprives them of excuse by saying of the women that they changed the natural use.
John Chrysostom (c. 349-407), Homilies on the Epistle to the Romans (trans. J. B. Morris and W. H. Simcox), in Nicene and Post-Nicene Fathers, ser. 1, vol. 11 (New York: Christian Literature Publishing Co., 1879) — Homily IV, on Romans 1:26-27
Reformed / Protestant
Calvin says that, after an intervening clause, he returns to what he had before stated about God's judgment. As the first example, he cites the dreadful crime of unnatural lust. This shows they not only abandoned themselves to beastly lusts but were degraded beyond beasts, reversing the whole order of nature.
John Calvin (1509-1564), Commentaries on the Epistle of Paul the Apostle to the Romans (trans. John Owen, Calvin Translation Society, 1849) — Commentary on Romans 1:26 ('God therefore gave them up')
Evangelical
Barnes identifies the sin in Romans 1:27 as the shameful sin of Sodom, called sodomy. He says it is scarcely credible that man would commit a crime so base and degrading without ample testimony. Perhaps no sin so deeply shows human depravity as this.
Albert Barnes (1798-1870), Notes, Explanatory and Practical, on the Epistle to the Romans (New York: Harper & Brothers, 1848) — Note on Romans 1:27 ('And likewise the men')