At the start of vayera, avraham is visited by no less than HaShem Himself, after Avraham's milah 3 days ago. Avraham sees 3 'men' in the distance and runs to greet them and invite them into his tent and welcome them. Our sages learn from here that hachnasas orchim is greater than receiving the shechinah - for Avraham chose hachnasas orchim over sitting there receiving HaShem's Presence.
So too does gemarra taanis (at very end) ask 'now that the mizbayach has gone, what atones for us?' And it answers
that our table atones; meaning when we invite someone in to sit at our table. It's our mini-alter!
And a crucial rule to remember here is that the halacha is that 'mitzvos tzrichos kavanah' ie mitzvos require intention.
This means that one must consciously think that 'I'm performing the torah mitzvah of hachnasas orchim' when performing that mitzvah (just like the other mitzvos eg tefillin, etc.
See shulchan aruch orach chaim 60;4) - for then can one connect up to the rewards and privileges of keeping a torah mitzvah.
And after all; we are guests in this world too, remember!.