Ibn Abī Najīḥ explained that Ibn ʿAbbās only meant: “I dislike fasting a single day on its own; rather, fast a day before it or a day after it.”
This is further confirmed by what al-Tirmidhī narrated from Ibn ʿAbbās (may Allah be pleased with them both): “The Messenger of Allah, peace and blessings be upon him, ordered the fasting of the day of ʿĀshūrāʾ—the tenth of Muḥarram.” Al-Tirmidhī commented, “This ḥadīth is ḥasan ṣaḥīḥ (good and sound).”
Saʿīd also reported in his Sunan—through Hishīm, from Ibn Abī Laylā, from Dāwūd ibn ʿAlī, from his father, from his grandfather Ibn ʿAbbās—that the Messenger of Allah, peace and blessings be upon him, said: “Fast on the day of ʿĀshūrāʾ and thus differ from the Jews; fast a day before it or a day after it.” Aḥmad likewise transmitted it with the wording: “Fast a day before it, or a day after it.”
(1) I could not locate the work entitled Fawaid of Dawud ibn Amr, nor could I find the statement attributed to Ibn Abi Najih in any of the sources I consulted.
(2) The word “hadith” is missing from copy B, whereas al-Tirmidhi explicitly says: “The hadith of Ibn Abbas is hasan sahih” (3/128).
(3) Al-Tirmidhi records the report in the Book of Fasting, chapter “Which day is Ashura,” hadith no. 754 (3/128), with the wording: “The Messenger of Allah, peace and blessings be upon him and his family, commanded fasting on Ashura, the tenth day.”
(4) The transmitter is Muhammad ibn Abd al-Rahman ibn Abi Layla al-Ansari al-Kufi; his biography has already been given—see the Biographical Index.
(5) Copy B reads: “from Ibn Abbas,” but the reading adopted here is more accurate.
(6) Copy B has: “a day after it,” whereas the correct wording is: “or.”
(7) The report is also narrated by Ibn Khuzayma in his Sahih (3/290–291), al-Bayhaqi in the Sunan (4/287), and Ahmad in the Musnad (1/241) with the formulation the author cites below. All three chains contain Ibn Abi Layla—a reliable transmitter, though one of weak retention. His biography has already been mentioned; see the Biographical Index.
(8) Copy B reads: “and a day,” but the correct reading is: “or.”
(9) Musnad Ahmad (1/241).