[1] At that time the Buddha, the Blessed One, was dwelling at Rājagaha, in the Veḷuvana, at the Kalandakanivāpa (the Squirrels' Feeding Ground). Now at that time the group-of-six bhikkhus (chabbaggiyā), while bathing, rubbed their bodies against trees — the thigh, the arm, the chest, and the back. People, seeing this, looked down upon them, criticized them, and spread it about, saying: "How can the ascetics, sons of the Sakyan, while bathing, rub their bodies against trees — the thigh, the arm, the chest, and the back — like wrestlers and boxers, like village dandies who pamper their skin?" Bhikkhus heard those people looking down upon them, criticizing them, and spreading it about … Then those bhikkhus reported this matter to the Blessed One.
Then the Blessed One, on that occasion, in that connection, had the community of bhikkhus assembled and questioned the bhikkhus: "Is it true, as is said, bhikkhus, that the group-of-six bhikkhus, while bathing, rub their bodies against trees — the thigh, the arm, the chest, and the back?"
"It is true, Blessed One."
The Buddha, the Blessed One, rebuked them: "Bhikkhus, it is unbefitting for those foolish men (moghapurisā), unsuitable, improper, unworthy of an ascetic, not allowable, not to be done. How, bhikkhus, can those foolish men, while bathing, rub their bodies against trees — the thigh, the arm, the chest, and the back? This, bhikkhus, does not conduce to the confidence of those without confidence …" Having rebuked them and given a talk on the Dhamma, he addressed the bhikkhus: "Bhikkhus, one who is bathing should not rub the body against a tree. Whoever should rub it commits an offense of wrong-doing (dukkaṭa)."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.