[148] Now at that time the group-of-six bhikkhus (chabbaggiyā) had all twenty nails polished. People looked down upon this, criticized it, and spread it about, … "just like householders who enjoy sensual pleasures" … They reported this matter to the Blessed One … "Bhikkhus, the twenty nails are not to be polished. Whoever should have them polished commits an offense of wrong-doing (dukkaṭa). I allow you, bhikkhus, to remove only the dirt."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.