General Overview

The Mitzvah of inviting guest to our homes is a well known one, and one which I was fortunate enough to have ingrained in my psyche from a very young age, thanks to my parent’s very open house policy. It behooves us to understand the greatness of this Mitzvah, as well as how to be a proper host and guest from a Halachic perspective.
Chazal have promised great blessings to those who welcome guests into their homes. It is counted amongst the mitzvos that one ‘receives the fruit from in this world, but his capital remains undiminished in the World to Come’. One who performs Hachnosas Orchim properly merits children, as we see from Avraham, who after feeding his guests was told that he will have children.Its also inferred from the Shunamite woman, who after hosting Elisha was promised a son. (Tanchuma Ki Setzei, Yalkut Shimoni Mishlei 4:837)

We find many examples of Hachnosas Orchim throughout Tanach. I’d like to list them, as well as the applicable lessons derived.

Noach – Was invited into the Ark by G-d. From here the Zohar learns that one should verify that his guest is not evil (Hashem first proclaimed Noach a Tzaddik and then told him to enter the ark). Additionally, onemust be invited, and cannot bring along his family unless explicitly allowed (Hashem instructed Noach to enter the Ark with his household).
Avraham –Left an audience with Hashem to go take care of his guests, teaching us that Hachnosas Orchim takes precedence over speaking to the Shechina. He would actively seek guests. He would give them food that was of better quality than they were used to receiving. He built roadside stands with food and drink for travelers. The Gemara in Bava Metzia 87 goes through the entire story of Avraham step by step and explains how the Jewish People were repaid by G-d for Avraham’s chesed. The actions performed by Abraham himself were repaid by Hashem himself, those delegated to a messenger were repaid via messenger.
Lot – Risked his life to invite guests to his home, who in turn saved Lot’s life.
Eliezer and Rivka – Eliezer devised a litmus test of eligibility to marry Yitzchak based on how the prospective young lady would invite him to the house. Rivka passed with flying colors, thus becoming a Matriarch of the Jewish People.
Yisro – Told his daughters to invite Moshe Rabeinu to their home, and was rewarded by having descendents who were members of the Sanhedrin.
Egypt – Although our sojourn there was far from pleasant, we are instructed to have gratitude to the Egyptians for hosting us. This is manifested in two ways: a) We must accept them as converts and b) the Gemara (Eruvin 118) writes that when Mashiach comes Egypt will want to bring him a gift, he will want to refuse it, but Hashem will instruct him to accept it “for they had provided refuge for My children”.
Amon and Moav – Did not offer us food when we passed by them on our journey through the desert. As a result their men are not allowed to join the Jewish nation, even though they descend from Lot and by right should be closer than others.
Shunamis – The Shunamite woman who provided a small room for Elisha when he passed through. As a result she was blessed with a son.
Yehonasan – Did not bring King David bread. This led to a chain of events that ultimately led to the massacre of the city of Nov and the death of Saul and three of his sons.
Micha – Avoided having his name placed in tis rightful spot on the notorious list of people who have no share in the World to Come, because he offered bread to all wayfarers.
The False Prophet – A false prophet misled Ido Hanavi, and caused him to violate the Word of G-d. But since he had given him food he merited true prophecy.
Iyov – had a house that was open on four sides and was known for his hospitality. Although the Gemara reports that he did not measure up to Avraham Avinu’s standards, it’s obvious that he excelled in this mitzvah.

Who is considered a Halachic Guest?

Although it is commendable for one to have many guests, there is a criterion that needs to be met in order to be considered a Halachic guest.
The Rema (333:1) explains that a Halachic guest is one who is sleeping at his house, or is sleeping at someone else’s house (not his own) and you are inviting them for a meal. Such a meal is considered a Seudas Mitzvah. The Mishna Berura adds that one may invite others to honor his Halachic guest and that would also supersede the above Rabbinic prohibitions.
The guest can be rich or poor, although with a poor guest one has the added benefit of Tzedaka.
If one accepts payment for hosting guests it is not considered fulfillment of the mitzvah (Kaf Hachaim 333)
There are certain halachos that are affected by guests:
The Gemara relates that having guests is equal, or perhaps greater than, going to learn Torah. The Chofetz Chaim writes that if one is on their way to learn and a guest arrives, if no one else is available to take care of the guests he should postpone his learning to take care of the guests.
There are certain secondary Rabbinic prohibitions that are suspended on Shabbos in order to do a Mitzvah, these would be suspended for a Halachic guest as well. The Mishna Berura adds that one may invite others to honor his Halachic guest and that would also supersede these Rabbinic prohibitions.

One can salt his meat for less time than usual if he has waiting guests

How to Host

The Chofetz Chaim (Ahavas Chesed 3:2) explains that the story of Avraham was given to us to understand how to properly host guests. Some of the lessons:
Offer water to wash up
Before offering food, offer rest
If the guest is rushing, don’t delay them
Bring each dish as it is ready
Include your children
Walk the guest out
He then adds other dinim that he collected from other Seforim:
Greet your guests smilingly
Don’t tell them all your financial problems – portray yourself as financially secure so that they don’t feel badly about eating from your food.
Don’t watch them eat so as not to embarrass them.
Put your guests in your best beds.
Walk them out; give them directions to get them where they’re going. The Rambam writes that this is the most important part of the Mitzvah and one who is lazy about this is considered paramount to a murderer. [As deduced from the Eglah Erufah incident]. The Chazon Ish said that in a place where there are other people in the street he may not be obligated.
The minimum one should escort his guests is 8 feet outside of the house.
If possible designate a room in your home as a ‘guest room’.
Additionally:
One should not invite someone he knows will refuse the invitation in order to score ‘points’ with them. (Chullin 94a)
The Gemara says a woman has a better read on the guests than a man
One isn’t obligated to trust their guests (Kallah 9 – see story there)

How to be a Guest

One must be invited and wanted
Stay in the same place every time unless they don’t want you.
One should not feed his hosts children without express permission
A guest may invite another guest (Bava Basra 98b) however Chazal refer to this practice as despicable (Derech Eretz Zuta 8)
A good guest recognizes the difficulties the host has gone through to host him (Berachos 58a)
One should inquire as to the welfare of the host’s household
A guest is obligated to follow all the directives of their host (excluding a directive to leave, according to one version in the Gemara) (Pesachim 86b)
There is a special blessing that is to be recited by a guest during Birkas Hamazon for the host. This is obligatory (Shulchan Aruch OC 201)

Communal Obligation

There is a communal obligation to host all guests. Members of the community can ‘force’ each other to have guests.