Abud-Darda' (May Allah be pleased with him) reported:
I heard the Messenger of Allah (ﷺ) saying, "Whenever a Muslim supplicates for his (Muslim) brother in his absence, the angels say: 'May the same be for you too'."[Muslim]. (ID)
App reference (ID): Book 17, Hadith 30 (ID)
Arabic/English book reference (ID): Book 17, Hadith 1494 (ID)