אמר רב יהודה אמר רב גדולה הכנסת אורחין מהקבלת פני שכינה..... א"ר יוחנן ששה דברים אדם אוכל פירותיהן בעולם הזה והקרן קיימת לו לעולם הבא ואלו הן הכנסת אורחין וביקור חולים ועיון תפלה והשכמת בית המדרש והמגדל בניו לתלמוד תורה והדן את חברו לכף זכות
Rab Judah said in Rab's name: Hospitality to travelers is greater than welcoming the presence of the Shechinah (God's presence),...R. Judah b. Shila said in R. Assi's name in R. Johanan's name: There are six things, the fruit of which man eats in this world, while the reward remains for him for the world to come, They are: Hospitality to travelers, visiting the sick, meditation in prayer, early attendance at the house of study, raising one's children in the study of the Torah, and judging one's neighbour for their merits
RADAK on Genesis 18:3 *Rabbi David Kimchi; Spain 1160-1235
ויאמר אדוני, our sagesare of two minds as to the meaning of the word A-donay in this verse. Some say it is sacred, an attribute of G’d; others hold that it is profane... The sages who hold that the word a-donay here is sacred, explain that Avraham used the plural mode because he was addressing G’d Who had visited him, asking Him to wait until he had been able to perform the duty of being a good host to these travelers who had suddenly appeared at the entrance of his tent. The lesson to be derived from this is that the merit of welcoming guests and making them feel at home is even greater than the merit of welcoming G’d into one’s house.