Is there any special Du`a'-ul-Istiftah (opening supplication when starting the Prayer) for supererogatory night Prayer? If there is one, what is it?
What should a worshipper do after finishing Witr (Prayer with an odd number of units)?
Yes, there are many supplications reported in the opening of the Prophet's Salah (prayer) during night Prayer.
reported in his Sahih on the authority of
`Aishah (may Allah be pleased with her) that she said:
"Allah's Messenger (peace be upon him) used to commence the optional night prayer with: O Allah! Lord of Jibril (Gabriel), Mika’il (Michael), and Israfil, Creator of the Heavens and the Earth, Knower of the unseen and the seen, You are the Arbitrator between Your Servants in that which they have disputed. Guide me in that which they have differed, to the Truth, by Your Leave, for truly You guide whom You will to the Straight Path."
(Part No. 7; Page No. 186)
Abu Dawud and
Al-Nasa'y (may Allah be Merciful with them both) reported that
Ubay ibn Ka`b (may Allah be pleased with him) said that the Messenger of Allah (peace be upon him) used to say when pronouncing Taslim (salutation of peace ending the Prayer) of Witr Salah:
"Glory be to the King, the Most Holy."
He said in the narration reported by
"Glory be to the King, the Most Holy," three times prolonging the utterance of the last syllable."
This Hadith was reported by
Al-Nasa'y in his book entitled Al-Kubra
with a good chain of transmission. He said:
"He utters it aloud the third time."
This is one part of the narration reported from
`Abdul-Rahman ibn Abza (may Allah be pleased with him).
(may Allah be merciful to him) reported this Hadith with a good chain of transmission with the wording:
Glory be to the King, the Most Holy, Lord of the Angels and the Spirit.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.