1At Sāvatthī. Then the Venerable Radha approached the Blessed One, [n.239] DPPN 2:730 explains that he was a brahmin of Rājagaha who had become a monk in his old age. The Buddha declared him the foremost of those who could inspire ingenuity in others (etadaggaṁ paṭibhāṇakeyyānaṃ; AN I 25,15). He has two verses at Th 133–34 (= Dhp 13–14).
Spk: Whenever the Tathāgata saw this elder, a subtle topic occurred to him. Thus the Blessed One taught him the Dhamma in various ways. In this saṁyutta, two vaggas have come down by way of questions, a third by way of request, and a fourth by way of intimate discourse (upanisinnakakathā, lit. "sitting nearby talk"). sn.iii.189 paid homage to him, sat down to one side, and said to him: "Venerable sir, it is said, ‘Māra, Māra.’ In what way, venerable sir, might Māra be?" [n.240] Spk: Here "Māra" is a metaphor for death and the aggregates (maraṇa-māra, khandha-māra).

2"When there is form, Radha, there might be Māra, or the killer, or the one who is killed. [n.241] MMāro vā assa māretā vā yo vā pana mīyati. Spk glosses māretā with māretabbo, but the word is clearly an agent noun with an active sense. Therefore, Radha, see form as Māra, see it as the killer, see it as the one who is killed. See it as a disease, as a tumour, as a dart, as misery, as real misery. Those who see it thus see rightly.

"When there is feeling … When there is perception … When there are volitional formations … When there is consciousness, Radha, there might be Māra, or the killer, or the one who is killed. Therefore, Radha, see consciousness as Māra, see it as the killer, see it as the one who is killed. See it as a disease, as a tumour, as a dart, as misery, as real misery. Those who see it thus see rightly."

3"What, venerable sir, is the purpose of seeing rightly?"

"The purpose of seeing rightly, Radha, is revulsion."

"And what, venerable sir, is the purpose of revulsion?"

"The purpose of revulsion is dispassion."

"And what, venerable sir, is the purpose of dispassion?"

"The purpose of dispassion is liberation."

"And what, venerable sir, is the purpose of liberation?"

"The purpose of liberation is Nibbāna." [n.242] Vimutti kho Rādha nibbānatthā. Spk: This "liberation of the fruit" is for the purpose of Nibbāna without clinging (phalavimutti nām’ esā anupādānibbānatthā).

"And what, venerable sir, is the purpose of Nibbāna?"

"You have gone beyond the range of questioning, Radha. [n.243] This paragraph is also at SN48.42 (V 218,19–21) and MN I 304,20–22. Be consistently reads the verb as accayāsi (aorist of atiyāti), Se as ccasarā (aorist of atisarati). Ee's assa here and ajjhaparam below must stem from faulty manuscripts.
The last sentence is: Nibbānogadhaṃ hi Rādha brahmacariyaṃ vussati nibbānaparāyanaṃ nibbānapariyosānaṃ. Many translators take nibbānogadha to mean "the plunge into Nibbāna" or "merging with Nibbāna," which the commentaries encourage by connecting ogadha with ogāha, a plunge (from the verb ogāhati, to plunge into). But ogadha is actually a by-form of ogādha, from the verb ogadhati, which the commentaries treat as synonymous with patiṭṭhahati, "to be established." They confirm this link by consistently glossing ogadha with patiṭṭhā, support; hence my rendering "ground." For the references, see CPD, s.v. ogadha, ogādhati, ogāha, and the use of the word gādha, both literal and metaphorical, in I, v. 263. MW defines gādha (from the root gādh, to stand firmly) as a ground for standing on in water, a shallow place, a ford. You weren’t able to grasp the limit to questioning. For, Radha, the holy life is lived with Nibbāna as its ground, Nibbāna as its destination, Nibbāna as its final goal."

1Sāvatthinidānaṁ. Atha kho āyasmā rādho yena bhagavā tenupasaṅkami; upasaṅkamitvā bhagavantaṁ abhivādetvā ekamantaṁ nisīdi. Ekamantaṁ nisinno kho āyasmā rādho bhagavantaṁ etadavoca:

2"‘Māro, māro’ti, bhante, vuccati. Kittāvatā nu kho, bhante, māro"ti? "Rūpe kho, rādha, sati māro vā assa māretā vā yo vā pana mīyati. Tasmātiha tvaṁ, rādha, rūpaṁ māroti passa, māretāti passa, mīyatīti passa, rogoti passa, gaṇḍoti passa, sallanti passa, aghanti passa, aghabhūtanti passa. Ye naṁ evaṁ passanti te sammā passanti.

Vedanāya sati … saññāya sati … saṅkhāresu sati … viññāṇe sati māro vā assa māretā vā yo vā pana mīyati. Tasmātiha tvaṁ, rādha, viññāṇaṁ māroti passa, māretāti passa, mīyatīti passa, rogoti passa, gaṇḍoti passa, sallanti passa, aghanti passa, aghabhūtanti passa. Ye naṁ evaṁ passanti, te sammā passantī"ti.

3"Sammādassanaṁ pana, bhante, kimatthiyan"ti?

"Sammādassanaṁ kho, rādha, nibbidatthaṁ".

"Nibbidā pana, bhante, kimatthiyā"ti?

"Nibbidā kho, rādha, virāgatthā". "Virāgo pana, bhante, kimatthiyo"ti?

"Virāgo kho, rādha, vimuttattho". "Vimutti pana, bhante, kimatthiyā"ti?

"Vimutti kho, rādha, nibbānatthā". "Nibbānaṁ pana, bhante, kimatthiyan"ti?

"Accayāsi, rādha, pañhaṁ, nāsakkhi pañhassa pariyantaṁ gahetuṁ. Nibbānogadhañhi, rādha, brahmacariyaṁ vussati, nibbānaparāyanaṁ nibbānapariyosānan"ti.

Paṭhamaṁ.