The Prophet (peace_be_upon_him) said: Any person who offers prayer at night regularly but (on a certain night) he is dominated by sleep will be given the reward of praying. His sleep will be…

The Prophet (peace_be_upon_him) said: Any person who offers prayer at night regularly but (on a certain night) he is dominated by sleep will be given the reward of praying. His sleep will be almsgiving.
Source: HOTD