Khuddakavatthukkhandhaka

Vinayapiṭaka · Cūḷavagga (2) · Vol. 7 · Section 82

[82] Now at that time, bhikkhus, while walking back and forth on the walking-path (caṅkama), fell off. They reported this matter to the Blessed One. "Bhikkhus, I allow a railing (vedikā) for the walking-path."

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 7 · Section 233 — Senāsanakkhandhaka