Sayyiduna Ibn Umar (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) said: "The prayers of the day and night are in sets of two rak‘ahs." Some narrators said: "Two by two rak‘ahs."
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1497
Hadith Takhrijاس حدیث کی سند صحیح ہے۔ دیکھے: [أبوداؤد 1326] ، [ابن حبان 2482] ، [موارد الظمآن 636]
Brief Explanation
(Commentary on Hadith 1496)
Voluntary prayers (nafl salah) should be performed two by two units (rak‘ah), as is established from the aforementioned hadith. Some people have said that during the day, four units should be performed, and during the night, two by two units. Some scholars have stated that in the phrase “salat al-layl wa’l-nahar” (prayer of the night and day), the word “wa’l-nahar” (and the day) is not reliably preserved. And Allah knows best.