The Iftitah 6 (for Tahajjud)

The Prophet PBUH would say (as an opening supplication in shalaat) when rising from sleep to perform prayers during the night (shalaatul lail / tahajjud ):

O Allah, to You belongs all praise, You are the Light of the Heavens and the Earth and all that is within them.

To You belongs all praise, You are the Sustainer of the Heavens and the Earth and all that is within them.

To You belongs all praise, You are Lord of the Heavens and the Earth and all that is within them.

To You belongs all praise, and the Kingdom of the Heavens and the Earth and all that is within them.

To You belongs all praise, You are the King of the Heavens and the Earth and all that is within them.

You are the truth, Your promise is true, Your Word is true, and the Day in which we will encounter You is true, the Garden of Paradise is true and the Fire is true, and the Prophets are true, Muhammad PBUH is true and the Final Hour is true.

O Allah, unto You i have submiteed, and upon You i have relied, and in You i have believed, and to You i have turned in repentance, and over You i have disputed, and to You i have turned for judgment.

So forgive me for what has come to pass of my sins and what will come to pass, and what i have hidden and what i have made public.

You are Al-Muqaddin and Al-Muakhhir. None has the right to be worshipped except You, You are my Deity,none has the right to be worshipped except You.

Meaning of Al-Muqaddim and Al-Muakhir:
Allah puts forward and favours whom He wills from amongst His creation just as He defers and holds back whom He wills in accordance to His wisdom. E.g. Favouring man over the rest of creation, favouring the Prophets over the rest of mankind, favouring Muhammad PBUH over all the Prophets and Messengers...etc