Prophet sallallahu alaihi wa sallam said,
"If ppl knew the reward of Isha and Fajr prayers in jamaat,
they would come to offer them even if they had to crawl."
Bukhari
Prophet sallallahu alaihi wa sallam said,"No prayer is harder for the hypocrites than the Fajr and the Isha prayers."
Bukhari 1.626
`Uthman bin `Affan reported: I heard the Messenger of Allah 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]
“Angels come to you in shifts by night and by day. They meet at salaat al-fajr and salaat al-‘asr, then those who had stayed with you at night ascend, and are asked by the One Who knows better than they: ‘How did you find My servants?’ They say, ‘We left them when they were praying, and we came to them when they were praying.’” (Reported by al-Bukhaari, al-Fath, 2/33).