Abu Saeed Khudri reported,
A man came after the Messenger of Allah ﷺ had already prayed, so he said, "Which of you will earn a reward by praying with this man?" A man stood up and prayed with him.
Tirmidhi 220
Sahihحدثنا هناد حدثنا عبدة عن سعيد بن أبي عروبة عن سليمان الناجي البصري عن أبي المتوكل
عن أبي سعيد قال
جاء رجل وقد صلى رسول الله ﷺ فقال أيكم يتجر على هذا فقام رجل فصلى معه
[Sahih]. Ibn Abu Shayba narrated it, 2/322, no. 7096, from Abdah bin Sulayman with similar wording. Abu Dawud narrated it, no. 574, through another route from Naji. Ibn Khuzayma graded it sahih, no. 1632, as did Ibn Hibban, no. 436, and Hakim, 1/209, and Dhahabi, and Hafiz in Fath al-Bari, 2/142. It has a corroborating narration in Daraqutni, 1/276, with a good chain, as acknowledged by Zaylai.On this topic there is also a narration from Abu Umama [Ahmad, 5/254, 269] and from Abu Musa, though I did not find it, and it may refer to the hadith in Ibn Majah, no. 1972, and from Hakam bin Umayr [Ibn Adi in Kamil, 5/1890].It appears in Marasil by Abu Dawud that the man is Abu Bakr Siddiq 