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AN 9.20 discusses a hierarchy of meritorious deeds. Superior to feeding a community of bhikkhus (but inferior to taking refuge) is building a dwelling (vihara) to the Sangha of the “four quarters.” What is the Sangha of the four quarters? Does this mean people attained to the 4 stages of awakening? Or the community of all the Buddha’s followers, including monks, nuns, laymen, and laywomen? Or something else?
Any input is appreciated 
Well, the Pali used is ‘cātuddisaṃ saṃghaṃ’ which Thanissaro Bhikkhu translates as ‘Community of the four directions’, which seems to be correct.
To my mind that indicates that the proposed building would be meant for the use of all monks from any (? Buddhist?) community in general, not just the community which the Buddha was heading. Eg. If the Buddha was staying at Jetavana, then the community at Rajgir would be outside the sima, and hence considered as a separate community headed by the senior monk there.
Interestingly, the Chinese parallel T73 uses a term that Google translates as ‘house used to recruit monks’. … but I don’t know if that’s correct, since I don’t read Chinese! Perhaps @cdpatton can help?
DN 31 shows that the four quarters definitely refers to the four cardinal directions, north, south, east and west, but what these may symbolize in the case of the sangha is not so clear. One suggestion is that they may not be symbolic at all, but refer to the fact that unlike today, monks in the Buddha’s time were constantly travelling and only converged on a vihara during the rains retreat, therefore the vihara was open to all such travellers. This is one of the greatest differences between the ancient and modern sanghas and has ramifications in terms of exposure to both conventional reality and wilderness, which then would have been much greater.
Details aside, the significant feature of AN 9.20 is that it is one of the few occasions where insight meditation is recommended for lay adherents subject to mundane right view.
"If one were to develop even for just a finger-snap the perception of inconstancy, that would be more fruitful than the gift "
The sangha of the dollar?
Thanks, everyone, for the responses so far. Something to note: in the previous “meritorious deed,” i.e., feeding the Sangha, it’s clear that the mendicant Sangha (as Bhante Sujato translates) is what’s intended. The precise word is “bhikkhusaṃghaṃ.” By contrast, with this deed about building a dwelling, there is no explicit mention of bhikkhus. It’s just “The Sangha of the four quarters/directions.” Dunno what to make of that.
EDIT: I should add another observation. The previous meritorious deed also says this mendicant sangha is “headed by the Buddha.” By contrast, it does not say the Sangha of the 4 directions is headed by the Buddha.
It looks to me like only T74 and MA 155 has this expression. “Four quarters” is an old way of saying “the regions in each of the four directions.” Perhaps it refers to the practice in ancient times of building public places for travelers to stay. The Buddhist sangha travelled around, so maybe here it would be a hostel just for travelling monks and nuns.
I believe it refers to the entire monastic sangha. The term is found in a couple of places in the Theravada Vinaya:
“Well now, do you, householder, establish these sixty dwelling-places for (the use of) the Order of the four quarters, present and to come.”
“Very well, Lord,” and the (great) merchant of Rājagaha, having answered the Lord in assent, had those sixty dwelling-places established for (the use of) the Order of the four quarters, present and to come.
Now at that time a certain monk who had many goods, many requisites, came to pass away. They told this matter to the Lord. He said: “Monks, the Order is the owner of the bowl and robes of a monk who has passed away. But truly those who tend the sick are of great service. I allow you, monks, to give through the Order the three robes and the bowl to those who tended the sick; to distribute through the Order that is present whatever few goods, few requisites are there; but whatever many goods, many requisites are there, these are for the Order of the four quarters—those who have come in, those who have not come in—they are not to be disposed of, not to be divided up.”
From Sujato’s Blog:
The main paradigm is that of a monastery given to the Sangha of the Four Quarters. This means all Buddhist monastics, past and future.
From VINAYA: Ownership and Administration of Monasteries, by Ajahn Brahm:
In the time of the Buddha, when a lay Buddhist offered lands of buildings, or money for such things, to establish a monastery, they would dedicate it to The Sangha of the Four Quarters Present and Yet to Come . The Sangha of the four quarters present and yet to come means ALL properly ordained monks and nuns.
The “Sangha of the four quarters” is a conventional phrase that refers to the monastic community in a general sense, rather than the specific monastics in a particular monastery.
(My reply overlapped with Christopher!)