Q.I would like to know the Hadith regarding the reward for performing the Esha and Fajr Salah in the Masjid?

A. In Bukhari, Volume 1, Book 11, Number 626:
Narrated Abu Huraira: The Prophet said, “No prayer is harder for the hypocrites than the Fajr and the ‘Isha’ prayers and if they knew the reward for these prayers at their respective times, they would certainly present themselves (in the mosques) even if they had to crawl.” The Prophet added, “Certainly I decided to order the Mu’adh-dhin (call-maker) to pronounce Iqama and order a man to lead the prayer and then take a fire flame to burn all those who had not left their houses so far for the prayer along with their houses.”