Witr Prayer

Dear scholars, As-Salamu `alaykum. I would like to know if the Witr Prayer is obligatory or Sunnah. Jazakum Allah khayran.

Dear Sheikh, As-Salamu `alaykum. My question is about witr prayer: I know that witr prayer is three rak`ahs. But I heard that it can be one rak`ah. Can you please provide me any reference for one rak`ah witr prayer (if any). Jazakum Allah khayran.

As-salamu 'alaykum wa rahmatu Allahi wa barakatuh, I have read in hadith that the prophet sallalahu 'alayhi wa sallam said that tahajjud prayer should be by twos and then conclude with one. My question is, is the final one the witr? Can we conclude with 3 rak'aahs of witr after the tahajjud? Because i might pray witr 3 rak'aahs usual with du'aa Qunoot, or i might pray witr with 2 rak'aahs with tasleem and then pray final one. But what i'm saying is i always would pray witr 3 rak'aahs. I appreciate your help. Jazaka Allahu khayr, wassalam.