When he decided to fight the enemy face to face at Siffin
Nahj al-Balāgha|Volume 1|Book 1|Chapter 171
[الدعوة للقتال :] أَيْنَ الْمَانِعُ لِلذِّمَارِ، وَالْغَائِرُ عِنْدَ نُزُولِ الْحَقَائِقِ مِنْ أَهْلِ الحِفَاظِ؟! العَارُ وَرَاءَكُمْ، وَالْجَنَّةُ أَمَامَكُمْ!
[Calling men to battle :] Where are those who protect honour, and those self-respecting persons who defend respectable persons in the time of hardship? Shame is behind you while Paradise is in front of you.