After brotherly love comes love for strangers or, you could call this, soul-winning love. Some the commentators say that this is about entertaining the travelling preachers and other travelling Christians.
What a sad thing if God cannot use us, because we are not available. He cannot use us in ministering to anyone else because we are one hundred percent of the time engaged with converted friends. We never have a moment to notice the stranger in need. Or, maybe there is a different problem: the Lord would not want the stranger to get hospitality in that home because their conversation is too frivolous, or even borders on the worldly, or they only take guests in order to show off or to put them right. They want to find out all the little things they do not have right in their theology or their understanding, and descend on them like a ton of bricks.
Look at the oblique promise in these words: ‘For thereby some have entertained angels unawares.’ Why say that, if it was not likely that we might be used of God in some special way, in our speaking to others and entertaining them? Why say it, if it is not a great hint that God may use us and bless us, unawares? That youngster who you are speaking to, may just be one of those who is in the very shy phase. A stumbling youngster with no social graces perhaps, inarticulate. Yet as the result of your hospitality or conversation, that stumbling, inarticulate youngster may turn into somebody who is a stalwart for the Lord, such a burden-bearer in future years, somebody who takes a stand and has such spiritual strength. You are unawares; you would never imagine it from first impact, first impression. God may use that hospitality, as others once extended to us.