Upaddhasutta 4.1

4.1

Tadamināpetaṃ, ānanda, pariyāyena veditabbaṃ yathā sakalamevidaṃ brahmacariyaṃ, yadidaṃ—kalyāṇamittatā kalyāṇasahāyatā kalyāṇasampavaṅkatā.

And here’s another way to understand how good friends are the whole of the spiritual life.