Sahih Bukhari Volume 1, Book 10, Hadith 615

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ سُمَىٍّ، مَوْلَى أَبِي بَكْرٍ عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لَوْ يَعْلَمُ النَّاسُ مَا فِي النِّدَاءِ وَالصَّفِّ الأَوَّلِ، ثُمَّ لَمْ يَجِدُوا إِلاَّ أَنْ يَسْتَهِمُوا عَلَيْهِ لاَسْتَهَمُوا، وَلَوْ يَعْلَمُونَ مَا فِي التَّهْجِيرِ لاَسْتَبَقُوا إِلَيْهِ، وَلَوْ يَعْلَمُونَ مَا فِي الْعَتَمَةِ وَالصُّبْحِ لأَتَوْهُمَا وَلَوْ حَبْوًا ‏"‏‏

Narrated By Abu Huraira : Allah's Apostle said, "If the people knew the reward for pronouncing the Adhan and for standing in the first row (in congregational prayers) and found no other way to get that except by drawing lots they would draw lots, and if they knew the reward of the Zuhr prayer (in the early moments of its stated time) they would race for it (go early) and if they knew the reward of 'Isha and Fajr (morning) prayers in congregation, they would come to offer them even if they had to crawl."