The twenty-
It may be compared to a journey of Pasenadi from Sāvatthi to Sāketa, by means of relays of seven carriages.
It is said in the introduction to the sutta that Sāriputta had been awaiting the opportunity of a discussion with Puṇṇa ever since he heard the monks at Veḷuvana in Rājagaha speak of him to the Buddha in terms of the highest praise. However, this opportunity did not arise until later, when Puṇṇa visited Sāvatthi. Puṇṇa was unaware of the identity of Sāriputta until the end of his discourse (M.i.145‑51).
The Mahāvaṃsa Ṭīkā mentions (MT.552 f ) that once Ambapāsānavāsī Cittagutta taught this sutta to a very large assembly of monks and nuns at the Lohapāsāda in Anurādhapura, and in his exposition of the sutta included a short account of the relies enshrined in the Mahā Thūpa.
It has been suggested by Dr. Neumann that the upatisapasina mentioned in Asoka’s Bhabru Edict, refers to this sutta. However, see Rhys Davids, J.R.A.S.1893, and Mukherji, Asoka, 118 f., n.8.