Imam Al-Nawawi's Riyad-us-Saliheen
Chapter 192
Urging to Observe 'Isha' and Fajr Prayers in Congregation

1071. `Uthman bin `Affan (May Allah be pleased with him) reported: I heard the Messenger of Allah (sallallaahu ’alayhi wa sallam) saying: "One who performs `Isha' prayer in congregation, is as if he has performed Salat for half of the night. And one who performs the Fajr prayer in congregation, is as if he has performed Salat the whole night.''
[Muslim]

      The narration of At-Tirmidhi says: `Uthman bin Affan (May Allah be pleased with him) narrated that he had heard the Messenger of Allah (sallallaahu ’alayhi wa sallam) saying: "He who attends `Isha' in congregation, is as if he has performed Salat for half of the night; and he who attends `Isha' and Fajr prayers in congregation, is as if he has performed Salat for the whole night.''

Commentary: This Hadith tells us that the reward of performing `Isha' and Fajr prayers in congregation is so great that it equals the worship of the whole night.

1072.Abu Hurairah (May Allah be pleased with him)reported: The Messenger of Allah (sallallaahu ’alayhi wa sallam) said, "If they knew the merits of Salat after nightfall (`Isha') and the morning (Fajr) Salat, they would come to them even if they had to crawl to do so.''
[Al-Bukhari and Muslim]

     This is part of a long Hadith which has already been mentioned. See Hadith No. 1033.

1073. Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (sallallaahu ’alayhi wa sallam) said, "No Salat is more burdensome to the hypocrites than the Fajr (dawn) prayer and the `Isha' (night) prayer; and if they knew their merits, they would come to them even if they had to crawl to do so.''
[Al-Bukhari and Muslim].

Commentary: `Isha' and Fajr prayers were, and still are, very hard for the hypocrites for the reason that they performed Salat only to make a show of it and not for the fear of Allah. Therefore, Muslims should not show any laziness in them at all, lest they develop a resemblance with the hypocrites.