Ḥibbān and al-Ḥākim in "al-Mustadrak" as well, then he attributed it in another place in "al-Kabīr" (1/21/1) to Ibn al-Sunnī in "ʿAmal al-Yawm wa-al-Laylah" and al-Ṭabarānī in "al-Kabīr," and I did not see it in "al-Mustadrak" after reviewing it in "al-Birr," "al-Ṣilah," and "al-Adab." And Allāh knows best. Among the supporting evidences for the ḥadīth is what Aḥmad narrated (3/438) through the route of Ibn Lahīʿah, who reported from Zabān, from Sahl ibn Muʿādh, from his father, from the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) who said: "It is a duty upon one who stands over a gathering to greet them with peace, and it is a duty upon one who leaves a gathering to greet with peace." A man stood while the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) was speaking and did not greet with peace, so the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) said: How quickly he forgot! I say: This chain is weak, but it is acceptable as supporting evidence. It is strengthened by the fact that al-Bukhārī narrated it in "al-Adab al-Mufrad" (1009) through another route from Basṭām, who said: I heard Muʿāwiyah ibn Qurrah say: My father said to me: "O my son, if you are in a gathering from which you hope for good and you are hastened by a need, then say: Peace be upon you, for you will share with them in what they attain in that gathering. And no people sit in a gathering and then disperse from it without mentioning Allāh, except that it is as if they dispersed from a carcass of a donkey." Its chain is authentic, all its narrators are trustworthy, and even though it is mawqūf [stopped at a Companion], it is considered marfūʿ [elevated to the Prophet] because it is not said from personal opinion, especially since most of it has been authentically reported as marfūʿ. Its first part is mentioned in this ḥadīth of Abū Hurayrah, and the other part is also mentioned in his ḥadīth, which has been previously mentioned as number (77). See what precedes and follows it. Greeting with peace when leaving a gathering is a neglected etiquette in some countries, and those most deserving of reviving it are the people of knowledge and their students. It is appropriate for them, when they enter upon students in a classroom, for example, to greet with peace, and likewise when they leave. The first is not more deserving than the other, and this is part of spreading peace as commanded in the forthcoming ḥadīth: "Indeed, peace is a name from the names of Allāh, which He placed on the earth, so spread peace among you."