To the army before the Battle of Siffin
Nahj al-Balāgha|Volume 1|Book 2|Chapter 14
لَا تُقَاتِلُوهُمْ حَتَّى يَبْدَءُوكُمْ، فَإِنَّكُمْ بِحَمْدِ اللهِ عَلَى حُجَّةٍ، وَتَرْكُكُمْ إِيَّاهُمْ حَتَّى يَبْدَءُوكُمْ حُجَّةٌ أُخْرَى لَكُمْ عَلَيْهِمْ،
Do not fight them unless they initiate the fighting, because, by the grace of Allāh, you are in the right and to leave them till they begin fighting will be another point from your side against them.