Uposathasutta untranslated

Uposathasutta 02. One Uposatha-day, the Buddha, surrounded by the company of monks, was seated in the Migāramātupāsāda, in Sāvatthī. Looking round and finding them seated in silence, he spoke their praises, saying how some of them had won access to the Devas, some to Brahma, others to the Imperturbable (ānejja), and yet others to the Ariyan state. AN.ii.183f.

Uposathasutta 03. One uposatha-night, during the first watch, Ānanda approaches the Buddha and asks him to recite the Pātimokkha. Three times he asks, but the Buddha remains silent, and at last says that the assembly is impure. Mahā Moggallāna, who is present, looks round, and seeing there a monk given up to wicked ways, asks him to leave. On his refusing to do so, Moggallāna takes him by the hand and leads him away. Thereupon the Buddha proceeds to explain how, just as the sea is full of eight kinds of marvels, so is the Dhamma. AN.iv.204ff.

Uposathasutta 04. (v.l. Uposathaṅgasutta). Visākhā, having taken the uposatha vows, visits the Buddha at noontide in the Migāramātupāsāda. The Buddha explains to her that there are various ways of observing the uposatha; these he describes as the herdsman’s uposatha, the uposatha of the naked ascetics and the uposatha of the Ariyans. AN.i.206f.

Uposathasuttā 01. Suttas dealing with questions asked by monks of the Buddha as to why certain Nāgas (egg-born, womb-born, moisture-born and born without parents) should keep the fast day, divesting themselves of their Nāga forms! The Buddha replies that they do so because they wish to be born in happy states SN.iii.241f.