كتاب الجهاد والسير
Fighting for the Cause of Allah (Jihaad)
Chapter: The Imam should order the people to do only within their ability
باب عَزْمِ الإِمَامِ عَلَى النَّاسِ فِيمَا يُطِيقُونَ
Sahih al-Bukhari 2964

Narrated `Abdullah:

Today a man came to me and asked me a question which I did not know how to answer. He said, "Tell me, if a wealthy active man, well-equipped with arms, goes out on military expeditions with our chiefs, and orders us to do such things as we cannot do (should we obey him?)" I replied, "By Allah, I do not know what to reply you, except that we, were in the company of the Prophet (ﷺ) and he used to order us to do a thing once only till we finished it. And no doubt, everyone among you will remain in a good state as long as he obeys Allah. If one is in doubt as to the legality of something, he should ask somebody who would satisfy him, but soon will come a time when you will not find such a man. By Him, except Whom none has the right to be worshipped. I see that the example of what has passed of this life (to what remains thereof) is like a pond whose fresh water has been used up and nothing remains but muddy water."

حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ أَبِي وَائِلٍ، قَالَ قَالَ عَبْدُ اللَّهِ ـ رضى الله عنه ـ لَقَدْ أَتَانِي الْيَوْمَ رَجُلٌ فَسَأَلَنِي عَنْ أَمْرٍ مَا دَرَيْتُ مَا أَرُدُّ عَلَيْهِ، فَقَالَ أَرَأَيْتَ رَجُلاً مُؤْدِيًا نَشِيطًا، يَخْرُجُ مَعَ أُمَرَائِنَا فِي الْمَغَازِي، فَيَعْزِمُ عَلَيْنَا فِي أَشْيَاءَ لاَ نُحْصِيهَا‏.‏ فَقُلْتُ لَهُ وَاللَّهِ مَا أَدْرِي مَا أَقُولُ لَكَ إِلاَّ أَنَّا كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم فَعَسَى أَنْ لاَ يَعْزِمَ عَلَيْنَا فِي أَمْرٍ إِلاَّ مَرَّةً حَتَّى نَفْعَلَهُ، وَإِنَّ أَحَدَكُمْ لَنْ يَزَالَ بِخَيْرٍ مَا اتَّقَى اللَّهَ، وَإِذَا شَكَّ فِي نَفْسِهِ شَىْءٌ سَأَلَ رَجُلاً فَشَفَاهُ مِنْهُ، وَأَوْشَكَ أَنْ لاَ تَجِدُوهُ، وَالَّذِي لاَ إِلَهَ إِلاَّ هُوَ مَا أَذْكُرُ مَا غَبَرَ مِنَ الدُّنْيَا إِلاَّ كَالثَّغْبِ شُرِبَ صَفْوُهُ وَبَقِيَ كَدَرُهُ‏.‏
Reference : Sahih al-Bukhari 2964
In-book reference : Book 56, Hadith 174
USC-MSA web (English) reference : Vol. 4, Book 52, Hadith 209
  (deprecated numbering scheme)