Hebrews 6:19-20
For indeed, if a man say that he is on the list of the Clergy, or calls himself a priest, then busy yourself [to enquire], make much ado: since in that case the communicating without enquiry is not without danger. For the danger is about matters of importance, for thou dost not give but receive. But if he want food, make no enquiry.
Enquire, if you will, how Abraham showed hospitality towards all who came to him. If he had been over-curious about those who fled to him for refuge, he would not have “entertained angels.” For perhaps not thinking them to be angels, he would have thrust them too away with the rest. But since he used to receive all, he received even angels.
What? Is it from the life of those that receive [your bounty] that God grants you your reward? Nay [it is] from your own purpose, from your abundant liberality; from your loving-kindness; from your goodness. Let this be [found], and you shall attain all good things, which may we all attain, through the grace and lovingkindness of our Lord Jesus Christ, with whom to the Father and together with the Holy Ghost, be glory, power, honor, now and for ever and world without end. Amen.
Source: Homilies on the Epistle to the Hebrews (New Advent)