As for Aḥmad, al-Ṭabarānī’s teacher, I have not found a biographical notice for him. It is likely to be found in Ibn ʿAsākir’s History, so whoever is able should consult it. This hadith has a supporting report from the hadith of Abū Hurayrah, attributed to the Prophet, with similar wording but without the addition. Its wording has previously appeared under no. 1326.
It was transmitted by Muslim (8/155), Aḥmad (2/308 and 323), and al-Ḥākim (4/435–436), who declared it authentic according to the conditions of the two Shaykhs. Al-Dhahabī agreed with him. Both of them, however, erred in considering it an omission from Muslim, for he did transmit it, as you have seen. Al-Haythamī likewise erred in citing it in al-Majmaʿ after the hadith under discussion, saying: “Al-Bazzār transmitted it, and its narrators are those of the authentic collections.”
1894 — “Al-Salām, the greeting of peace, is one of Allah’s Names, which He has placed upon the earth; so spread it among yourselves. When a Muslim man passes by a group of people, greets them with peace, and they return his greeting, he has a degree of merit over them. But if they do not return it, one better and more excellent than they will return it to him.”
Al-Bazzār (no. 1999) transmitted it: al-Faḍl ibn Sahl narrated to us; Muḥammad ibn Jaʿfar al-Madāʾinī narrated to us; Warqāʾ narrated to us, from al-Aʿmash, from Zayd ibn Wahb, from the Prophet (peace and blessings be upon him). He also said: Aḥmad ibn ʿUthmān ibn Ḥakīm narrated to us; ʿAbd al-Raḥmān ibn Sharīk narrated to us, from his father, from al-Aʿmash, from Zayd ibn Wahb, from ʿAbd Allāh, from the Prophet (peace and blessings be upon him), who said it. He said: “More than one narrator related it as a report attributed to the Companion, while Warqāʾ, Sharīk, and Ayyūb ibn Jābir attributed it to the Prophet.”
I say: Its second chain of transmission is weak because of the poor retention of Sharīk—namely, Ibn ʿAbd Allāh al-Qāḍī—and of his son. Al-Ḥāfiẓ said concerning the father: “He was truthful, but made many errors; his retention changed after he assumed the office of judge.”