544 – On the authority of Ḥafṣah, Mother of the Believers (may Allah be pleased with her), that the Prophet ﷺ said, “Whoever does not determine the fast during the night before dawn has no fast.” It was narrated by the Five, while al-Tirmidhī and al-Nasā’ī inclined toward judging it mawqūf, and Ibn Khuzaymah and Ibn Ḥibbān authenticated it as marfūʿ.
Al-Dāraqutnī also recorded the wording, “No fast is valid for the one who did not resolve upon it in the night.” (1)

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Degree of authenticity:
The ḥadīth is sound (ṣaḥīḥ).
It was produced by Abū Dāwūd, al-Dāraqutnī, al-Ṭaḥāwī, and al-Bayhaqī through the chain of ʿAbd Allāh ibn Wahb back to Ḥafṣah, and by Imām Aḥmad through the chain of Ḥasan ibn Mūsā. All its narrators are those relied upon by the two Shaykhs except Ibn Luhayʿah, and his ḥadīths are reliable whenever one of the three ʿAbd Allāhs transmits from him, as is the case here.
Regarding whether it is marfūʿ or mawqūf: some scholars preferred the mawqūf stance—among them al-Bukhārī, Abū Dāwūd, al-Nasā’ī, al-Tirmidhī, Abū Ḥātim, and al-Bayhaqī—while others upheld the marfūʿ attribution, including Ibn Ḥazm, al-Khaṭṭābī, ʿAbd al-Ḥaqq, Ibn al-Jawzī, and al-Shawkānī. Al-Bayhaqī and al-Dāraqutnī remarked, “Its transmitters are trustworthy,” Ibn Ḥazm reinforced its standing, and al-Ḥākim declared it authentic.

Glossary of the ḥadīth:
– “Whoever does not determine the fast” (man lam yubayyit al-ṣiyām): The verb bayyata means “to arrange something by night.” Here it signifies failing to intend the obligatory fast during the night, and thus the fast is invalid.