Riyad Us-Saliheen (Gardens of the Righteous)

Chapter 190
The Excellence of waiting for As-Salat (The Prayer)

1061. Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, "Everyone among you will be deemed to be occupied in Salat (prayer) constantly so long as Salat (the prayer) detains him (from worldly concerns), and nothing prevents him from returning to his family but Salat.''
[Al-Bukhari and Muslim].

Commentary: This Hadith tells us the merits of waiting for Salat. As long as a person sits in mosque waiting for Salat, all his time is reckoned as being in the state of Salat and so eligible for the same reward.

1062. Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, "The angels supplicate in favour of one of you so long as he remains in the place where he has performed Salat (prayer) in a state of Wudu'. They (the angels) say: `O Allah! Forgive him, O Allah! Have mercy on him.'''
[Al-Bukhari].

Commentary: This Hadith has inducement for sitting in the place where one has performed Salat, provided one keeps his Wudu' intact, when a person does so, angels pray Allah to forgive him and have mercy upon him.

1063. Anas (May Allah be pleased with him) reported: Once the Messenger of Allah (PBUH) delayed the night prayer (`Isha') till midnight. He (PBUH) turned to us after Salat (prayer) and said, "The people slept after performing their Salat, but you who waited, will be accounted as engaged in Salat throughout the period of your waiting.''
[Al-Bukhari].

Commentary: We learn from this Hadith that it is an act of merit and reward to sit and wait for the Imam and the Jama`ah (congregation) and one who does so will be treated as one who is engaged in Salat. We also learn from this Hadith that if a person performs Salat when its time is due, it is quite fair, although in that case he will not get the reward of waiting for the Imam and the Jama`ah.