Hadith 1040:2
Rawh narrated to us, Sa'id ibn Abi 'Arubah narrated to us, from Qatadah, from 'Abd al-Rahman ibn Salamah al-Khuza'i, from his uncle, who said: We went out early with the Messenger of Allah, peace and blessings of Allah be upon him, on the morning of 'Ashura, and we had already eaten lunch. He said, "Have you fasted this day?" We said, "We have already eaten lunch." He said, "Then complete the remainder of your day."
حدثنا روح، حدثنا سعيد بن أبي عروبة، عن قتادة، عن عبد الرحمن بن سلمة الخزاعي، عن عمه قال: غدونا مع رسول الله صلى الله عليه وسلم صبيحة عاشوراء وقد تغدينا فقال: " أصمتم هذا اليوم؟ "، قال: قلنا: قد تغدينا، قال: " فأتموا بقية يومكم "