Sahih Adab al-Mufrad

It is narrated from Safwan bin Abdullah bin Safwan. Darda bint Abu Darda was in his marriage. He narrates that (once) I reached them (Abu Darda) in Syria and saw that Umm Darda was at home and Abu Darda was not there. Umm Darda asked me: "Do you intend to perform Hajj this year?" I said: "Yes." She said: "Pray for good for us, the Prophet (ﷺ) used to say: 'The supplication of a Muslim man for his Muslim brother in his absence is accepted. An angel is appointed over his head; when he prays for good for his brother, the angel says: Ameen, and may you have the same.'" Safwan narrated that after this, I met Abu Darda in the market, and he narrated the same. He used to narrate this (hadith) from the Prophet (ﷺ).