Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) sent a man from the tribe of Aslam to his people on the day of Ashura, to order them to fast on this day. He said: I do not think I will reach them before they have eaten. He (peace and blessings be upon him) said: "Whoever of them has eaten, let him fast the rest of the day."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8407
Sayyidah Rubayyi' bint Mu'awwidh bin Afra' (may Allah be pleased with her) narrates that on the morning of Ashura the Messenger of Allah (peace and blessings be upon him) sent a messenger to the villages of the Ansar around Madinah: "Whoever began the morning fasting should complete his fast, and whoever began the morning not fasting (muftir) should complete the rest of the day." She says: After that we used to fast on it, and we would make our young children fast as well. We would make toys of wool for them and take them to the mosque, and when one of them cried for food, we would give him that (toy) until it was time to break the fast.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8408
Sayyidah Aishah (may Allah be pleased with her) narrates: The day of Ashura was a day on which Quraysh fasted in the Days of Ignorance (Jahiliyyah), and the Messenger of Allah (peace and blessings be upon him) also used to fast on it before prophethood. When he (peace and blessings be upon him) came to Madinah, he (peace and blessings be upon him) fasted on it and ordered that it be fasted. Then when Ramadan was made obligatory, that became the obligation, and the day of Ashura was left. So "whoever wishes may fast on it, and whoever wishes may leave it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8409
Sayyidah Aishah (may Allah be pleased with her) narrates that the Messenger of Allah (peace and blessings be upon him) "used to order the fasting of the day of Ashura" before Ramadan was made obligatory. When the fasting of Ramadan was made obligatory, whoever wished would fast, and whoever wished would not fast.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8410
Abdur-Rahman bin Yazid (may Allah have mercy on him) narrates that Sayyiduna al-Ash'ath bin Qays (may Allah be pleased with him) came to Sayyiduna Abdullah (may Allah be pleased with him) on the day of Ashura while he was eating. He said: O Abu Muhammad! Come near and eat. He said: Is today not the day of Ashura? He said: Do you know what the day of Ashura is? It was only a day on which the Messenger of Allah (peace and blessings be upon him) used to fast before (the fasting of) Ramadan was revealed; then when Ramadan was revealed, he (peace and blessings be upon him) left it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8411
Ibn Umar (may Allah be pleased with them both) narrates that the people of the Days of Ignorance (Jahiliyyah) used to fast on the day of Ashura. The Messenger of Allah (peace and blessings be upon him) also fasted on it, and so did the Muslims, before Ramadan. When Ramadan was made obligatory, the Messenger of Allah (peace and blessings be upon him) said: "Ashura is one of the days of Allah; whoever wishes may fast on it, and whoever wishes may not."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8412
Sayyiduna Jabir bin Samurah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) used to order us to fast on the day of Ashura, would encourage us to do so, and would make us keep to it. When Ramadan was made obligatory, he (peace and blessings be upon him) neither ordered us, nor forbade us, nor made us keep to it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8413
Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) narrates that the day of Ashura was a day that the Jews venerated and celebrated, so the Messenger of Allah (peace and blessings be upon him) said: "You fast on it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8414
Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: When the Messenger of Allah (peace and blessings be upon him) came to Madinah, he saw that the Jews fasted on Ashura, so he (peace and blessings be upon him) asked them. They said: This is the day on which Allah Almighty made Musa prevail over Pharaoh. He (peace and blessings be upon him) said: "You are closer to Musa; you fast on it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8415