The Discourse about Kassapa

ekaṁ samayaṁ Bhagavā Rājagahe viharati,
at one time the Fortunate One was dwelling near Rājagaha,

Veḷuvane Kalandakanivāpe. Dr. Mark Allon points out in Style and Function that the openings of the discourses often have a rhythmic structure (which he calls "loose veḍha" (e.g. pg. 246), but which I think would be better termed prose gaṇa). If we read mĕ (which for syntactic reasons is preferable to Allon’s reading sutam), the opening in this discourse can be scanned as follows:
−−¦⏑⏑−¦−−¦⏑⏑−¦⏑⏑−¦−⏑⏑¦−⏑⏑¦⏑⏑
Evaṁ mĕ sutaṁ: ekaṁ samayaṁ Bhagavā Rājagahe viharati
−¦⏑⏑−¦⏑−⏑¦⏑⏑−¦−
Veḷuvane Kalandakanivāpe.
It should be noted, however, that not all the openings scan as well as this.
in Bamboo Wood, at the Squirrels’ Feeding Place.

Tena kho pana samayena āyasmā Mahākassapo
Then at that time venerable Mahākassapa

Pipphaliguhāyaṁ viharati, ābādhiko dukkhito bāḷhagilāno.
was dwelling in the Pepper Cave, and was afflicted, suffering, and very sick.

Atha kho āyasmā Mahākassapo aparena samayena
Then venerable Mahākassapa at another time

Atha kho āyasmato Mahākassapassa
^o Then this occurred to venerable Mahākassapa

tamhā ābādhā vuṭṭhitassa etad-ahosi: etad-ahosi, this occurred, is an idiom, more literally: this was to venerable Mahākassapa.
when he arose from that affliction:

“Yannūnāhaṁ Rājagahaṁ piṇḍāya paviseyyan”-ti.
“Well now, I should enter Rājagaha for alms.”

pañcamattāni devatāsatāni The splitting of the numerals as here ...pañca... ...satāni... is a characteristic of these constructions, perhaps used for emphasis. ussukkaṁ āpannāni honti
five hundred devatās were ready and eager

āyasmato Mahākassapassa piṇḍapātapaṭilābhāya. This is a dative of purpose used in the sense of the infinitive, which occurs quite frequently in the texts; it normally has the dative ending in - āya.
to offer almsfood to venerable Mahākassapa.

tāni pañcamattāni devatāsatāni paṭikkhipitvā,
after refusing those five hundred devatās,

pubbanhasamayaṁ The accusative here overlaps with the locative in meaning. Similarly with Rājagahaṁ below, where we may translate: entered into Rājagaha for alms.

Note also that piṇḍāya is an infinitive-like dative of purpose, Commentary: piṇḍāya pāvisī ti piṇḍapātatthāya pāvisi. nivāsetvā, pattacīvaram-ādāya,
having dressed in the morning time, after picking up his bowl and robe,

yena daḷiddavisikhā kapaṇavisikhā pesakāravisikhā.
(going) to the poor streets, to the wretched streets, to the weaver’s streets.

Addasā kho Bhagavā āyasmantaṁ Mahākassapaṁ
The Fortunate One saw venerable Mahākassapa

yena daḷiddavisikhā kapaṇavisikhā pesakāravisikhā.
(going) to the poor streets, to the wretched streets, to the weaver’s streets.

Atha kho Bhagavā, etam-atthaṁ viditvā,
Then the Fortunate One, having understood the significance of it,

tāyaṁ velāyaṁ imaṁ udānaṁ udānesi:
on that occasion uttered this exalted utterance:

“Anaññaposiṁ aññātaṁ, The Commentary states that anaññaposiṁ here can also mean "not nourished by another", though it is hard to see how such an epithet can apply to an almsman!

The Commentary defines aññāta as meaning either well-known, or its opposite, unknown ! Udānavarga (33-23) reads: Ananyapoṣī hy ājñātā, which suggests that the Sanskrit redactor(s) understood that the first meaning was the original. dantaṁ sāre patiṭṭhitaṁ,
“Not nourishing another, well-known, controlled, established in the essential,

Khīṇāsavaṁ Āsava is literally an outflow or overflow; pollutant, which is the translation adopted here, is semantically identical in meaning, from Latin polluere, to wash over, to defile. vantadosaṁ: tam-ahaṁ brūmi brāhmaṇan”-ti.
With pollutants destroyed, rid of faults: him I call a brāhmaṇa.”