Prayer at Night (Tahajjud) 
Bukhari :: Book 2 :: Volume 21 :: Hadith 252
Narrated 'Abdullah bin 'Amr bin Al-'As:
Allah's Apostle said to me, "O 'Abdullah! Do not be like so and so who used to pray at night and then stopped the night prayer."
Prayer at Night (Tahajjud)
Bukhari :: Book 2 :: Volume 21 :: Hadith 252
Narrated 'Abdullah bin 'Amr bin Al-'As:
Allah's Apostle said to me, "O 'Abdullah! Do not be like so and so who used to pray at night and then stopped the night prayer."