Language:
كتاب الجهاد والسير
56  
Fighting for the Cause of Allah (Jihaad)
(73)
Chapter: The superiority of guarding (Muslims from infidels)
(73)
بَابُ فَضْلِ رِبَاطِ يَوْمٍ فِي سَبِيلِ اللَّهِ
Sahih al-Bukhari 2892

Narrated Sahl bin Sa`d As-Sa'di:

Allah's Messenger (ﷺ) said, "To guard Muslims from infidels in Allah's Cause for one day is better than the world and whatever is on its surface, and a place in Paradise as small as that occupied by the whip of one of you is better than the world and whatever is on its surface; and a morning's or an evening's journey which a slave (person) travels in Allah's Cause is better than the world and whatever is on its surface."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُنِيرٍ، سَمِعَ أَبَا النَّضْرِ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ أَبِي حَازِمٍ، عَنْ سَهْلِ بْنِ سَعْدٍ السَّاعِدِيِّ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ رِبَاطُ يَوْمٍ فِي سَبِيلِ اللَّهِ خَيْرٌ مِنَ الدُّنْيَا وَمَا عَلَيْهَا، وَمَوْضِعُ سَوْطِ أَحَدِكُمْ مِنَ الْجَنَّةِ خَيْرٌ مِنَ الدُّنْيَا وَمَا عَلَيْهَا، وَالرَّوْحَةُ يَرُوحُهَا الْعَبْدُ فِي سَبِيلِ اللَّهِ أَوِ الْغَدْوَةُ خَيْرٌ مِنَ الدُّنْيَا وَمَا عَلَيْهَا ‏"‏‏.‏
Reference : Sahih al-Bukhari 2892
In-book reference : Book 56, Hadith 107
USC-MSA web (English) reference : Vol. 4, Book 52, Hadith 142
  (deprecated numbering scheme)