كتاب الأذان
Call to Prayers (Adhaan)
Chapter: The first row
باب الصَّفِّ الأَوَّلِ
Sahih al-Bukhari 720, 721

Narrated Abu Huraira:

The Prophet (ﷺ) said, "Martyrs are those who die because of drowning, plague, an Abdominal disease, or of being buried alive by a falling building." And then he added, "If the people knew the Reward for the Zuhr prayer in its early time, they would race for it. If they knew the reward for the `Isha' and the Fajr prayers in congregation, they would join them even if they had to crawl. If they knew the reward for the first row, they would draw lots for it."

حَدَّثَنَا أَبُو عَاصِمٍ، عَنْ مَالِكٍ، عَنْ سُمَىٍّ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ الشُّهَدَاءُ الْغَرِقُ وَالْمَطْعُونُ وَالْمَبْطُونُ وَالْهَدْمُ ‏"‏‏.‏ وَقَالَ ‏"‏ وَلَوْ يَعْلَمُونَ مَا فِي التَّهْجِيرِ لاَسْتَبَقُوا ‏{‏إِلَيْهِ‏}‏ وَلَوْ يَعْلَمُونَ مَا فِي الْعَتَمَةِ وَالصُّبْحِ لأَتَوْهُمَا وَلَوْ حَبْوًا، وَلَوْ يَعْلَمُونَ مَا فِي الصَّفِّ الْمُقَدَّمِ لاَسْتَهَمُوا ‏"‏‏.‏
Reference : Sahih al-Bukhari 720, 721
In-book reference : Book 10, Hadith 115
USC-MSA web (English) reference : Vol. 1, Book 11, Hadith 688
  (deprecated numbering scheme)