Soorah Ikhlaas & Kafiroon
Ibn al-Qayyim -Rahimahullaah- said:
‘I heard Shaykh ul-Islaam Ibn Taymeeyah saying:
‘The Sunnah of Fajr follows the path of the first of the actions [of the day] and the Witr prayer is the seal.
This is why the Prophet -sallAllaahu alayhi wa sallam- used to pray the Sunnah of Fajr and the Witr with the Two Soorahs of Ikhlaas [Soorah Ikhlaas and Kafiroon]
These two Soorahs are comprehensive of Tawheed of knowledge and action, and Tawheed of knowing about Allaah [Rooboobeeyah & Asmaa wa Sifaat] and intention [worship] and Tawheed of Belief and intent of worship for Allaah [Eelaheeyah].
[Zaad al-Ma’ad 1 p.316 ]