I say: This is a chain of transmission all of whose narrators are trustworthy except Hibban ibn ‘Ali, who is weak despite his learning and virtue. Perhaps he erred in its chain of transmission; otherwise, the text of the hadith is authentic, for it has corroborating reports:

The first is from Umm al-Darda’, who said: My master—that is, her husband Abu al-Darda’—told me that he heard the Messenger of Allah, peace and blessings be upon him, say: “When a man supplicates for his brother in his absence, the angels say: ‘Amin, and for you the same.’” It was narrated by Muslim (8/86) and Abu Dawud (1534), the latter’s wording being cited here, through the route of Musa ibn Tharwan, who said: Talhah ibn ‘Ubayd Allah ibn Kurayz told me; Umm al-Darda’ told me.

Ahmad also narrated it (6/452) through another route from Talhah, with the same wording, but he did not mention Abu al-Darda’ in its chain of transmission, thus making it a report from Umm al-Darda’! Muslim and Ahmad (5/195 and 6/452) then narrated it, as did Ibn Majah (2895) and Abu al-Shaykh in Hadiths of Abu al-Zubayr from Narrators Other than Jabir (17/1), through the route of Safwan ibn ‘Abd Allah ibn Safwan—who was married to Umm al-Darda’—who said: “I came to Syria and went to Abu al-Darda’s house, but I did not find him there; I found Umm al-Darda’. She said: ‘Do you intend to perform Hajj this year?’ I replied: ‘Yes.’ She said: ‘Then supplicate to Allah for good for us, for the Prophet, peace and blessings be upon him, used to say: The supplication of a Muslim for his brother in his absence is answered. At his head is an angel appointed to attend him; whenever he supplicates for good for his brother, the angel appointed to him says: “Amin, and for you the same.”’” He said: “Then I went out to the market and met Abu al-Darda’, who said the same to me, relating it from the Prophet, peace and blessings be upon him.”

Note: Al-Manawi did not come across Ibn ‘Adi’s chain of transmission, and therefore made no comment about it. However, he said: “Muslim and Abu Dawud also narrated it from Umm al-Darda’ the Younger, who was a Successor; thus, according to them both, it is mursal.” This is what he said, as though he had overlooked her statement in the first narration: “My master told me.”