Genesis 19:5

ונדעה אותם AND WE SHALL KNOW THEM — with homosexuality, as in "who have not known a man" (Bereishit Rabbah).

And they cried to Lot, and said to him, Where are the men who entered with thee tonight? Bring them out to us, and we will lie with them.

AND WE SHALL KNOW THEM. Their intention was to stop people from coming among them, as our Rabbis have said, for they thought that because of the excellence of their land, which was as the garden of the Eternal, many will come there, and they despised charity. Lot, however, came to them with his riches and wealth [and was given permission to live in Sodom because] he either asked permission of them, or that they accepted him in honor of Abraham.
Now Scripture testifies that this was the intent of the people of Sodom, as it is said, Behold, this was the iniquity of thy sister Sodom: pride, fullness of bread, and careless ease was in her and in her daughters; neither did she strengthen the hand of the poor and needy. The verse stating, And the men of Sodom were wicked and sinners against the Eternal exceedingly, really means that they continued provoking and rebelling against Him with their ease and the oppression of the poor. It is this thought which Scripture expresses by saying, And they were haughty, and committed abomination before Me; therefore I removed them when I saw it.
In the opinion of our Rabbis, all evil practices) were rampant among them. Yet their fate was sealed because of this sin — i.e., they did not strengthen the hand of the poor and needy — since this sin represented their usual behavior more than any other. Besides, since all peoples act righteously towards their friends and their poor, there was none among all the nations who matched Sodom in cruelty.
Know that the judgment of Sodom was due to the superiority of the Land of Israel since Sodom is part of the inheritance of the Eternal, and it does not suffer men of abominations. And just as it later vomited out a whole nation on account of their abominations, so it now anticipated and saw that this entire people behaved worse than all nations towards Heaven and mankind. It thus laid waste heaven and earth for them, and the land was destroyed forever, never to be restored, since they became haughty on account of the goodness that was bestowed on them. The Holy One, blessed be He, thus made Sodom a token against the rebellious children, that is, against the children of Israel who were destined to inherit it, even as He warned them: The whole land thereof is brimstone, and salt, and a burning… like the overthrow of Sodom and Gomorrah, Admah and Zeboiim, which the Eternal overthrew in His anger, and in His wrath. For there have been among nations those who were evil and exceedingly sinful, and yet He did not do to them as He did to Sodom. However it was all on account of the superiority of this land for there is the temple of the Eternal. I plan to explain this in Seder Achrei Moth, if He Who taketh life and giveth life will sustain me in life.

ונדעה אותם. A euphemism for committing sodomy with these strangers. The same expression as a euphemism is also found in Judges 19,22.

ויקראו...ונדעה אותם, who these people are, and how such people had dared to enter our town at night in spite of our reputation. The word ונדעה is a euphemism for the intention to kill these people, just as it is in Judges 19,22 as reported by a party involved there in 20,5 Other commentators believe that the euphemism concerns the intention of sodomising these men.