«إن الرجل إذا صلى مع الإمام حتى ينصرف كتب له قيام ليلة»
The Prophet (peace and blessings be upon him) said:
"Indeed, when a man keeps praying with the imam until he (the imam) finishes, the reward of a whole night of worship (standing in prayer) is written for him."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 1615