The Messenger of Allah ﷺ said, "A man will intercede for two men and three men, and a man will intercede for a single man."
قال رسول الله ﷺ: إن الرجل ليشفع للرجلين والثلاثة، والرجل للرجل.
No references are available.
Bazzar narrated it in Kashf Astar (3473), and Ibn Khuzayma in Tawhid (624), through various routes from Abdul-Razzaq, who reported, "Maamar informed us, from Thabit, that he heard Anas bin Malik say (so he mentioned it)." Its chain of transmission is sahih.