Nahj al-Balāgha

Hadith 539
warfare-jihad
ومن كلام له (عليه السلام) قاله لاصحابه في ساعة الحرب بصفين
Amīr al-mu’minīn’s address to his followers on the battlefield of Ṣiffīn About supporting the weak and the low-spirited during the fighting
Source: al-Sharīf al-Raḍī