Al-Adab Al-Mufrad #1012

Mu'awiya ibn Qurra said, "My father told me, 'If you sit in a gathering expecting good to come from, but then something occurs which makes you leave, say, 'Peace be upon you,' and you will share in any good that they obtain in that gathering. There are no people who sit in a gathering and then split up without Allah having been mentioned, but that it is as if they were leaving the corpse of a donkey.'"