that when the crescent of Sha‘bān was obscured, the Prophet ﷺ would count thirty days and then begin fasting (1). This hadith of hers has been rejected on the grounds that, had it been authentic, she would not have acted contrary to it; her fasting was thus taken as grounds for impugning the hadith. This is not so, however: she did not regard fasting that day as obligatory, but fasted it only as a precaution. She understood from the Prophet’s ﷺ practice and command that fasting did not become obligatory until the full count had been completed. Neither she nor Ibn ‘Umar understood this to mean that fasting that day was impermissible.

This is the most balanced view on the issue, reconciling the hadiths and the reports from the Companions. It is supported by what Ma‘mar narrated from Ayyūb, from Nāfi‘, from Ibn ‘Umar: the Prophet ﷺ said concerning the crescent of Ramadan:

“When you see it, begin fasting, and when you see it, end your fast. If it is obscured from you, reckon thirty days (2).”

Ibn Abī Rawwād narrated it from Nāfi‘, from Ibn ‘Umar, with the wording: “If it is obscured from you, complete the count of thirty.” Mālik and ‘Ubayd Allāh narrated it from Nāfi‘, from Ibn ‘Umar, with the wording: “Reckon its duration” (3).

This indicates that Ibn ‘Umar did not understand the hadith to require completing thirty days, but rather to permit it. Thus, when he fasted on the thirtieth day, he chose one of two permissible courses as a precaution. Further evidence is that, had he—may Allah be pleased with him—understood the Prophet’s ﷺ words to mean, “Reckon twenty-nine days, then fast,” as those who deem fasting that day obligatory maintain, he would have instructed his family and others to do so. He would not have confined himself to fasting it personally without instructing others to do so or explaining (4) that this was obligatory for everyone.