Sahih Bukhari
Prayer at Night (Tahajjud)
Volume: 002 / Book Number: 021 / Hadith Number: 244
Narrated Samura bin Jundab:
The Prophet said in his narration of a dream that he saw, "He whose head was being crushed with a stone was one who learnt the Quran but never acted on it, and slept ignoring the compulsory prayers."