From:
Theravāda Vinaya Theravāda Collection on Monastic Law
Mahāvibhaṅga The Great Analysis
Sekhiyakaṇḍa The chapter on training
Ujjagghikavagga The subchapter on laughing loudly
19. Sīsappacālakasikkhāpada 19. The training rule on swaying the head
Tena samayena buddho bhagavā sāvatthiyaṁ viharati jetavane anāthapiṇḍikassa ārāme. At one time the Buddha was staying at Sāvatthī in the Jeta Grove, Anāthapiṇḍika’s Monastery.
Tena kho pana samayena chabbaggiyā bhikkhū sīsappacālakaṁ antaraghare gacchanti sīsaṁ olambentā …pe…. At that time the monks from the group of six were swaying and tilting their heads while walking in inhabited areas. …
“Na sīsappacālakaṁ antaraghare gamissāmīti sikkhā karaṇīyā”ti. “‘I will not sway my head while walking in inhabited areas,’ this is how you should train.”
Na sīsappacālakaṁ antaraghare gantabbaṁ. One should not sway one’s head while walking in an inhabited area;
Sīsaṁ paggahetvā gantabbaṁ. one should walk keeping one’s head straight.
Yo anādariyaṁ paṭicca sīsappacālakaṁ antaraghare gacchati sīsaṁ olambento, āpatti dukkaṭassa. If a monk, out of disrespect, sways and tilts his head while walking in an inhabited area, he commits an offense of wrong conduct.
Anāpatti—There is no offense:
asañcicca …pe… if it is unintentional;
ādikammikassāti. if he is the first offender.
Navamasikkhāpadaṁ niṭṭhitaṁ. The ninth training rule is finished.