Khuddakavatthukkhandhaka

Vinayapiṭaka · Cūḷavagga (2) · Vol. 7 · Section 40

[40] Now at that time bhikkhus put their bowls away in the heat, and the color of the bowls was spoiled. They reported this matter to the Blessed One. "Bhikkhus, a bowl should not be put away in the heat; whoever should put one away commits an offense of wrong-doing (dukkaṭa). I allow, bhikkhus, that a bowl be warmed in the heat for a short while and then put away."

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 7 · Section 54 — Khuddakavatthukkhandhaka