Bhaya: Fear
Fear is the mind's bracing against harm. The bolts go across the door at evening, though the thing being guarded against has already happened on a hill outside town, and the mind keeps rehearsing it after dark. Fear works like a hand gripping too tightly: the harder the grip, the less it can hold or receive.
Saṅgha: The gathered community
Saṅgha is the body of practitioners held together by a shared training. Assembled is the one thing they get right that night, because terror usually scatters people and these did not scatter. A locked room with company in it is still better than a locked room alone, and it is company that keeps the training alive when the teacher is gone.
Iddhi: Unimpeded movement
Among the powers described in the early texts is passing through a wall as if through open space. Locked doors are the limit of what these frightened people could arrange for themselves, and the arrival simply does not use the door. The bolt was never what kept him out; the assumption that a bolt settles who may enter was.
Abhaya: The gift of safety
Abhaya is safety given to someone else. "Peace be to you" comes first, ahead of teaching, ahead of any word about the ones who ran off in the garden. Handing a lamp into a dark room settles the matter without any argument about the dark, and fear is left with nothing to work on.
Santi: Peace
Santi names the cooling of what was burning. The greeting is an ordinary one, the same words traded in any doorway in that city, and here it reports what has just walked into the room rather than wishing for something later. Peace of this kind is the fire going out indoors while the wind still blows outside, so it can arrive well before the streets are safe.