Sahih Muslim Book - 32, Hadith - 4636

وَحَدَّثَنِى إِبْرَاهِيمُ بْنُ سَعِيدٍ الْجَوْهَرِىُّ حَدَّثَنَا أَبُو أُسَامَةَ عَنْ مَالِكِ بْنِ مِغْوَلٍ عَنْ أَبِى حَصِينٍ عَنْ أَبِى وَائِلٍ قَالَ سَمِعْتُ سَهْلَ بْنَ حُنَيْفٍ بِصِفِّينَ يَقُولُ اتَّهِمُوا رَأْيَكُمْ عَلَى دِينِكُمْ فَلَقَدْ رَأَيْتُنِى يَوْمَ أَبِى جَنْدَلٍ وَلَوْ أَسْتَطِيعُ أَنْ أَرُدَّ أَمْرَ رَسُولِ اللَّهِ -صلى الله عليه وسلم- - مَا فَتَحْنَا مِنْهُ فِى خُصْمٍ إِلاَّ انْفَجَرَ عَلَيْنَا مِنْهُ خُصْمٌ.

It was narrated that Abu Wa'il said: I heard Sahl bin Hunayf at Siffin saying: Do not rely on your own opinions with regard to matters of religion, for I remember the day of Abu Jandal (i.e. Al-Hudaibiyah). If I could have gone against the command of the Messenger of Allah (s.a.w) (I would have done so). When we rely upon your opinion to solve a problem, another problem arises to take its place.