Hadith 42:71
Hasan Sahih (Al-Albani)
Qayla reported that a mans aid, "Peace be upon you, may Allah bless him and grant him peace." He said, "And peace be upon you and the mercy of Allah."
قَالَ أَبُو عَبْدِ اللهِ: وَقَالَتْ قَيْلَةُ: قَالَ رَجُلٌ: السَّلاَمُ عَلَيْكَ يَا رَسُولَ اللهِ، قَالَ: وَعَلَيْكَ السَّلاَمُ وَرَحْمَةُ اللهِ
Original Reference: Al-Adab Al-Mufrad 1034