[186] Now at that time, when bhikkhus sneezed, people would say, "Live, venerable sirs!" The bhikkhus, being scrupulous, did not speak in reply. People complained, criticized, and spread it about, saying, "How can the ascetics, sons of the Sakyan, when told 'Live, venerable sirs!' not speak in reply?" They reported this matter to the Blessed One. … "Bhikkhus, householders are given to auspicious observances. I allow, bhikkhus, a bhikkhu who is told by householders, 'Live, venerable sir,' to say, 'May you live long.'"
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.