Anupubbikathā

Vinayapiṭaka · Cūḷavagga (2) · Vol. 7 · Section 400

[400] Truly, he who, upon entering an assembly of harsh speakers, does not tremble, who does not fail in his speech, nor conceal the message, who declares it without hesitation, and when questioned does not become angry— a bhikkhu such as this is indeed worthy to go on a messenger's errand.

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.