A man came to the Prophet ﷺ and said, "Peace be upon you."The Prophet ﷺ said, "Ten."Then another man came and said, "Peace be upon you and the mercy of Allah."The Prophet ﷺ said, "Twenty."Then another came and said, "Peace be upon you and the mercy of Allah and His blessings."The Prophet ﷺ said, "Thirty."
حدثنا عبد الله بن عبد الرحمن والحسين بن محمد الحريري البلخي قالا حدثنا محمد بن كثير عن جعفر بن سليمان الضبعي عن عوف عن أبي رجاء
أن رجلا جاء إلى النبي ﷺ فقال السلام عليكم قال قال النبي ﷺ عشر ثم جاء آخر فقال السلام عليكم ورحمة الله فقال النبي ﷺ عشرون ثم جاء آخر فقال السلام عليكم ورحمة الله وبركاته فقال النبي ﷺ ثلاثون
Its isnad is hasan. Abu Dawud narrated it in the Book of Manners, Chapter on How to Give the Greeting, no. 5195, from Muhammad bin Kathir through this route, and Hafiz strengthened it in Fath al-Bari 6/11. It has a corroborating narration in Ibn Hibban (al-Ihsan), no. 493.On this subject there are also narrations from Abu Saeed (I could not find it), from Ali (Bazzar in Kashf Astar 2/418, no. 2001, and Ibn Sunni, no. 232), and from Sahl bin Hunayf (Abd bin Humayd, no. 470, and Tabarani in al-Kabir 6/76, no. 5563).