Dutiyakalyāṇamittasutta 
Dutiyakalyāṇamittasutta → dutiyakalyāṇamittasuttaṁ (bj); kalyāṇamittatā (pts1ed) Good Friends (2nd)

Sāvatthinidānaṁ.  At Sāvatthī.

“Ekadhammo, bhikkhave, bahūpakāro ariyassa aṭṭhaṅgikassa maggassa uppādāya.  “Mendicants, one thing helps give rise to the noble eightfold path.
Katamo ekadhammo?  What one thing?
Yadidaṁ—kalyāṇamittatā.  It’s good friendship.
Kalyāṇamittassetaṁ, bhikkhave, bhikkhuno pāṭikaṅkhaṁ—ariyaṁ aṭṭhaṅgikaṁ maggaṁ bhāvessati, ariyaṁ aṭṭhaṅgikaṁ maggaṁ bahulīkarissati.  A mendicant with good friends can expect to develop and cultivate the noble eightfold path.

Kathañca, bhikkhave, bhikkhu kalyāṇamitto ariyaṁ aṭṭhaṅgikaṁ maggaṁ bhāveti, ariyaṁ aṭṭhaṅgikaṁ maggaṁ bahulīkaroti?  And how does a mendicant with good friends develop and cultivate the noble eightfold path?
Idha, bhikkhave, bhikkhu sammādiṭṭhiṁ bhāveti rāgavinayapariyosānaṁ dosavinayapariyosānaṁ mohavinayapariyosānaṁ …pe… sammāsamādhiṁ bhāveti rāgavinayapariyosānaṁ dosavinayapariyosānaṁ mohavinayapariyosānaṁ.  It’s when a mendicant develops right view, right thought, right speech, right action, right livelihood, right effort, right mindfulness, and right immersion, which culminate in the removal of greed, hate, and delusion.
Evaṁ kho, bhikkhave, bhikkhu kalyāṇamitto ariyaṁ aṭṭhaṅgikaṁ maggaṁ bhāveti, ariyaṁ aṭṭhaṅgikaṁ maggaṁ bahulīkarotī”ti.  That’s how a mendicant with good friends develops and cultivates the noble eightfold path.”

Paṭhamaṁ.