Reference : Hisn al-Muslim 106

سُبْحَانَ اللَّهِ (ثلاثاً وثلاثين) 
وَالْحَمْدُ لِلَّهِ (ثلاثاً وثلاثين) 
وَاللَّهُ أَكْبَرُ (أربعاً وثلاثينَ)
Subḥānallāh, 
Wa ‘l-ḥamdu lillāh, 
Wallāhu Akbar.


Glory is to Allah (thirty-three times in Arabic), 
Praise is to Allah (thirty-three times),
Allah is the Most Great (thirty-four times)

Reference:
Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 7/71, Muslim 4/2091.

Chapter: Before sleeping