(33) The Book on Government
كتاب الإمارة
(34) Chapter: The virtue of Jihad and keeping watch over the frontier
(34) باب فَضْلِ الْجِهَادِ وَالرِّبَاطِ ‏‏
Sahih Muslim 1888 c 

A version of the tradition narrated on the authority of Ibn Shihab has a little differently worded ending. i. e." A man in a mountain valley." but did not mention" next to him a man who...."

وَحَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَبْدِ الرَّحْمَنِ الدَّارِمِيُّ، أَخْبَرَنَا مُحَمَّدُ بْنُ يُوسُفَ، عَنِ الأَوْزَاعِيِّ، عَنِ ابْنِ شِهَابٍ، بِهَذَا الإِسْنَادِ فَقَالَ ‏"‏ وَرَجُلٌ فِي شِعْبٍ ‏"‏ ‏.‏ وَلَمْ يَقُلْ ‏"‏ ثُمَّ رَجُلٌ ‏"‏ ‏.‏
Reference : Sahih Muslim 1888c
In-book reference : Book 33, Hadith 184
USC-MSA web (English) reference : Book 20, Hadith 4654
  (deprecated numbering scheme)