Salama reported,
The Messenger of Allah ﷺ instructed a man to announce on the day of Ashura, "Whoever has already eaten should complete the rest of the day fasting, and whoever has not eaten should fast."
Nasai 2323
Sahihأخبرنا محمد بن المثنى قال حدثنا يحيى عن يزيد قال
حدثنا سلمة
أن رسول الله ﷺ قال لرجل أذن يوم عاشوراء من كان أكل فليتم بقية يومه ومن لم يكن أكل فليصم
Bukhari narrated it in the Book of Solitary Reports, chapter "What the Prophet ﷺ used to send the commanders with," etc., hadith no. 7265, from the hadith of Yahya Qattan. Muslim narrated it in the Book of Fasting, chapter "Whoever eats on Ashura should refrain for the rest of his day," hadith no. 1135, from the hadith of Yazid bin Abu Ubayd, with the same wording. It is also found in Kubra, hadith no. 2630.* Salama is Ibn Akwa 