Thomas Aquinas, on Heb 13:2

“And hospitality do not forget; for by this some, being not aware of it, have entertained angels.”

“He says, do not neglect, because formerly, when they were prosperous, they were very hospitable; but now that they were poor and could not do so much, he exhorts them to continue to do as much as possible: 'Pursue hospitality' (Rom. 12:13). He makes special mention of hospitality, because a person who receives travelers does three acts of charity at once, because he receives and feeds and gives them drink: 'Using hospitality one towards another without murmuring' (1 Pt 4:9). He gives the reason when he says, for thereby some have entertained angels unawares, as in the case of Abraham and Lot (Gen. 18 & 19). Another version reads: 'By this, as unawares, they entertained angels,' because they did not believe that they were angels. This was also true in the beginning; hence, Abraham adored them, thinking that they were holy men sent from God. But he adored them with adoration called dulia, which is shown to saints; and he offered them food, as though they were men. But after he understood that they were angels in whom God was speaking, he spoke to them as to God, saying: 'This is not beseeming you who judge all the earth' (Gen. 18:25); and Lot in like manner.”

Imported from an open dataset — not yet checked against the printed edition.