The Prophet (May Allāh praise him and Peace be upon him) used to pray witr as three consecutive, unbroken raka‘āt (units of prayer). The evidence for this is the ḥadīth of Ubay Ibn Ka‘b in which he said: In the first rak‘ah, the Prophet (May Allāh praise him and Peace be upon him) would recite Sūrah Al-A‘lā (Sūrah no. 87). In the second, he would recite Sūrah Al-Kāfirūn (Sūrah no. 109). In the third rak‘ah, he would recite Sūrah Al-Ikhlāṣ (Sūrah no. 112). [This ḥadīth was graded as ṣaḥīḥ (authentic) by Al-Shaykh Al-Albānī in Ṣaḥīḥ Sunan Al-Nasāī]

•He would sometimes separate the shaf‘ (even number of raka‘āt) from the witr (odd number of raka‘āt). The evidence for this is that Ibn ‘Umar said: the Prophet (May Allāh praise him and Peace be upon him) would sometimes separate the shaf‘ (even number of raka‘āt) from the witr (odd number of raka‘āt) with a taslīm (saying salām) which he would say such that we could hear it.
[Reported by Al-Imām Aḥmad in Al-Musnad]