John Calvin Commentary Genesis 19:2

"and he said, Behold now, my lords, turn aside, I pray you, into your servant`s house, and tarry all night, and wash your feet, and ye shall rise up early, and go on your way. And they said, Nay; but we will abide in the street all night." — Genesis 19:2 (ASV)

Nay, but we will abide in the street. The angels do not immediately consent, so that they might more fully investigate the character of the holy man. For he was about to bring them to his own house, not merely to supply them with a supper, but also to defend them from the violence and harm of the citizens.

Therefore, the angels act as if it were safe to sleep in the public street, and thus they conceal their knowledge of the utter wickedness of the whole people. For if the gates of cities are shut to prevent the attacks of wild beasts and enemies, how wrong and absurd it is that those within should be exposed to even more severe dangers?

Therefore, the angels speak this way to make the wickedness of the people appear even greater. And Lot, by urging the angels to come to him to protect them from the widespread violence of the people, more clearly shows how careful he was of his guests, so that they would not suffer any dishonor or harm.