´Umm Salamah narrated:` "The Prophet would pray two Rak'ah after Al-Witr."
Related hadith on this topic
Explanation & Benefits
Shaykh Dr. Abdur Rahman Freywai
1:
According to Nawawi, the Prophet sallallahu alayhi wa sallam’s performing two units of prayer after Witr was to demonstrate permissibility.
He did not always do so,
nor could he have done so consistently, as he himself said:
“Make Witr the last of your night prayers (tahajjud),” so how could he himself act contrary to this?
Or, it may be understood that this was something specific to him,
and perhaps this is the reason that the scholars of the Ummah did not adopt this practice.
And Allah knows best.
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 471