Hadeeth:

“You should perform the Night Prayer, for indeed it is the (continuous) practice of the righteous (people) who were before you; it draws (you) close to your Lord, expiates evil deeds and stops (you) from sins.

[Reported by Al-Haakim (rahimahullaah) 1/308 and others, and declared Hasan by Shaikh Albaani (rahimahullaah) in ‘Irwaa Al-Ghaleel’ Number 452; Pages 199-200; Vol 2; Publisher: Maktabah Al-Islaamiy 2^nd  Ed. 1405 AH (Year 1985)]