I asked Abu Wail, "Did you take part in the battle of Siffin?" He said, 'Yes, and I heard Sahl bin Hunaif (when he was blamed for lack of zeal for fighting) saying, "You'd better blame your wrong opinions. I wish you had seen me on the day of Abu Jandal. If I had the courage to disobey the Prophet's orders, I would have done so. We had kept out swords on our necks and shoulders, for a thing which frightened us. And we did so, we found it easier for us, except in the case of the above battle (of ours).' "  

أَنْ أَرُدَّ أَمْرَ النَّبِيِّ ﷺ لَرَدَدْتُهُ وَمَا وَضَعْنَا أَسْيَافَنَا عَلَى عَوَاتِقِنَا لأَمْرٍ يُفْظِعُنَا إِلاَّ أَسْهَلْنَ بِنَا إِلَى أَمْرٍ نَعْرِفُهُ غَيْرِ أَمْرِنَا هَذَا  

When Sahl bin Hunaif returned from (the battle of) Siffin, we went to ask him (as to why he had come back). He replied, "(You should not consider me a coward) but blame your opinions. I saw myself on the day of Abu Jandal (inclined to fight), and if I had the power of refusing the order of Allah's Apostle then, I would have refused it (and fought the infidels bravely). Allah and His Apostle know (what is convenient) better. Whenever we put our swords on our shoulders for any matter that terrified us, our swords led us to an easy agreeable solution before the present situation (of disagreement and dispute between the Muslims). When we mend the breach in one side, it opened in another, and we do not know what to do about it."  

اتَّهِمُوا الرَّأْىَ فَلَقَدْ رَأَيْتُنِي يَوْمَ أَبِي جَنْدَلٍ وَلَوْ أَسْتَطِيعُ أَنْ أَرُدَّ عَلَى رَسُولِ اللَّهِ ﷺ أَمْرَهُ لَرَدَدْتُ وَاللَّهُ وَرَسُولُهُ أَعْلَمُ وَمَا وَضَعْنَا أَسْيَافَنَا عَلَى عَوَاتِقِنَا لأَمْرٍ يُفْظِعُنَا إِلاَّ أَسْهَلْنَ بِنَا إِلَى أَمْرٍ نَعْرِفُهُ قَبْلَ هَذَا الأَمْرِ مَا نَسُدُّ مِنْهَا خُصْمًا إِلاَّ انْفَجَرَ عَلَيْنَا خُصْمٌ مَا نَدْرِي كَيْفَ نَأْتِي لَهُ  

I heard Sahl b. Hunaif say at Siffin: O ye people, find fault with your (own) discretion. By Allah, on the Day of Abu Jandal (i. e. the day of Hudaibiya), I thought to myself that, if I could, I would reverse the order of the Messenger of Allah ﷺ (the terms of the truce being unpalatable). By Allah, we have never hung our swords on our shoulders in any situation whatsoever except when they made easy for us to realise the goal envisaged by us, but this battle of yours (seems to be an exception). Ibn Numair (in his version) did not mention the words:" In any situation whatsoever" (Using translation from Muslim 1785b)   

أَنْ أَرُدَّ أَمْرَ رَسُولِ اللهِ ﷺ لَرَدَدْتُهُ وَاللهِ مَا وَضَعْنَا سُيُوفَنَا عَلَى عَوَاتِقِنَا إِلَى أَمْرٍ قَطُّ إِلَّا أَسْهَلَ بِنَا إِلَى أَمْرٍ نَعْرِفُهُ إِلَّا أَمْرَكُمْ هَذَا»