The tribe of Aslam came to the Prophet ﷺ, and he asked, "Have you fasted today?"They replied, "No."He said, "Then complete the rest of your day in fasting and make it up later."
حدثنا محمد بن المنهال حدثنا يزيد بن زريع حدثنا سعيد عن قتادة
أن أسلم أتت النبي ﷺ فقال صمتم يومكم هذا قالوا لا قال فأتموا بقية يومكم واقضوه
No references are available.
Its chain of transmission is daif.Ahmad narrated it: 5/409, and Nasai in Kubra, no. 2851, 2852, from the hadith of Saeed bin Abu Aruba, through this route. Abdul-Rahman bin Maslamah is obscure, no one but Ibn Hibban has deemed him trustworthy, and Ibn Qattan considered him unknown.