[Explanation]
These narrations elucidate the excellence of the night prayer.
In the ḥadith of Abū Hurayrah (may Allah be pleased with him) the Prophet (peace and blessings be upon him) said, “The best fasting after Ramadan is the fasting observed in Allah’s month, Muḥarram.” Fasting the month of Ramadan is one of the pillars of Islam and is obligatory by unanimous agreement. Muḥarram is the most virtuous month for voluntary fasting; therefore fasting during Muḥarram is a recommended act, for it is the finest fast after the obligatory one.
The point we wish to highlight from this ḥadith is the statement: “And the best prayer after the prescribed prayers is the night prayer.” This is the decisive evidence: the night prayer is superior to voluntary prayers offered during the day, except for the regular sunnah prayers attached to the obligatory prayers, for those sunnahs are better than unrestricted night prayers. For example, the regular sunnah of ẓuhr is four rakʿahs—offered as two units followed by the salām—before the obligatory prayer, and two rakʿahs after it. These six rakʿahs are more excellent than six voluntary rakʿahs prayed at night because they are an emphasised sunnah connected to an obligation. As for unrestricted voluntary prayers, they are better at night than during the day; hence the Prophet said, “The best prayer after the obligatory prayers is the night prayer.”
As for the two reports from Ibn ʿUmar, they prove that the night prayer is offered two rakʿahs at a time; one may not offer four in a single set. Instead it must be two followed by the salām, then two followed by the salām. Imām Aḥmad (d. 241 AH) said, “If a person rises for a third rakʿah out of forgetfulness, his situation is like that of someone who stands for a third rakʿah in the dawn prayer.”
That is, he must sit back down; if he does not, his prayer is invalid. In practice, if you are praying at night in pairs of rakʿahs and you rise for a third through forgetfulness, you must return to the sitting position—even if you have already started reciting Sūrat al-Fātiḥah. Failing to do so renders the prayer invalid, because the Messenger of Allah (peace and blessings be upon him) said, “The night prayer is two by two,” meaning in pairs—except for the witr prayer, when a person offers it as three