Is the Witr prayer classified among the five obligatory daily prayers?

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The Witr prayer is not classified among the five obligatory prayers (Salawat al-Maktubah). Ali reported that Witr is not the sealing prayer, nor is it like the prescribed prayers. This is supported by the report of the Bedouin who asked the Prophet what Allah had mandated for him daily and nightly, and the response was only the five prayers, with the Prophet affirming, "There is nothing else upon you unless you volunteer (tatattu')."