Nasai

(1) From the above-mentioned narrations, it is understood that this narration is sometimes reported as the statement of Hafsah radi Allahu anha herself, sometimes as the saying of the Messenger of Allah sallallahu alayhi wa sallam, and sometimes as the statement of Ibn Umar radi Allahu anhu. Therefore, the hadith scholars differ regarding this narration. The renowned imams of hadith, such as Imam Bukhari, Imam Abu Dawud, Imam Nasa’i, Imam Tirmidhi, and Imam Ahmad rahimahumullah, consider this narration to be authentic in the mawquf form, meaning it is the statement of Hafsah or Ibn Umar radi Allahu anhum themselves and not narrated from the Messenger of Allah sallallahu alayhi wa sallam. However, Imam Ibn Khuzaymah, Imam Ibn Hibban, Imam Daraqutni, Imam Ibn Hazm, and Imam Hakim rahimahumullah have declared it authentic even in the marfu’ form, meaning it is also the statement of the Messenger of Allah sallallahu alayhi wa sallam. Even if, for argument’s sake, it is not accepted as authentically marfu’, it would still be considered as marfu’ in ruling, because the basis of this fatwa of Hafsah radi Allahu anha is not her own opinion or analogy; certainly, its basis can only be the statement of the Messenger of Allah sallallahu alayhi wa sallam. For further details, see: (Dhakheerat al-‘Uqba Sharh Sunan al-Nasa’i: 21/247-249). And Allah knows best.

(2) The intention (niyyah) for a voluntary fast (nafl) can also be made during the day.

(3) It is necessary to make the intention for an obligatory fast (fard) before the true dawn (subh sadiq). That is, the intention can be made any time after sunset until before the appearance of the true dawn.