Hadith 4:93
Umm Salama reported God’s messenger as saying, “When you are with one who is ill or dying speak good words, for the angels say Amen to what you say.” Muslim transmitted it.
وَعَنْ أُمِّ سَلَمَةَ قَالَتْ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِذَا حَضَرْتُمُ الْمَرِيضَ أَو الْمَيِّت فَقولُوا خيرا فَإِن الْمَلَائِكَةَ يُؤَمِّنُونَ عَلَى مَا تَقُولُونَ» . رَوَاهُ مُسْلِمٌ
Original Reference: Mishkat al-Masabih 1617