Musnad Ahmad 30:1513

Yunus ibn Muhammad narrated to us, Hammad—meaning Ibn Zayd—narrated to us, from Thabit, from Abu Rafi‘, from Abu Hurairah, that a black woman—or a man—used to sweep the mosque. The Messenger of Allah (ﷺ) missed them and asked about them. They said: "They have died." He said: "Why did you not inform me of that?" They said: "It was..." He said: "Show me to their grave." They showed him, so he came to their grave and prayed over them.