Mahāparinibbāna Sutta 1.6.13

1.6.13

Yāvakīvañca, bhikkhave, bhikkhū apaññattaṃ na paññapessanti, paññattaṃ na samucchindissanti, yathāpaññattesu sikkhāpadesu samādāya vattissanti, vuddhiyeva, bhikkhave, bhikkhūnaṃ pāṭikaṅkhā, no parihāni.

As long as the mendicants don’t make new decrees or abolish existing decrees, but proceed having undertaken the training rules as they have been decreed, they can expect growth, not decline.