Sunan an-Nasa'i, Volume 6, Book 47, Hadith 5039 (DarusSalam) ⓘ
It was narrated that Abu Sa'eed Al-Khudri said: "The Messenger of Allah [SAW] said: 'Soon the best wealth of a Muslim will be the sheep which follows in the mountain peaks and places where rainfall is to be found, fleeing with his religion from the tribulations.'"
أَخْبَرَنَا هَارُونُ بْنُ عَبْدِ اللَّهِ قَالَ حَدَّثَنَا مَعْنٌ ح وَالْحَارِثُ بْنُ مِسْكِينٍ قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ عَنْ ابْنِ الْقَاسِمِ قَالَا حَدَّثَنَا مَالِكٌ عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدِ اللَّهِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبِي صَعْصَعَةَ عَنْ أَبِيهِ عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُوشِكُ أَنْ يَكُونَ خَيْرَ مَالِ مُسْلِمٍ غَنَمٌ يَتَّبِعُ بِهَا شَعَفَ الْجِبَالِ وَمَوَاقِعَ الْقَطْرِ يَفِرُّ بِدِينِهِ مِنْ الْفِتَنِ
also referenced under: Hadith 5036 (Reference) & Book 47, Hadith 52 (In-Book)