Learning from history, al-Mahdi
Nahj al-Balāgha|Volume 1|Book 1|Chapter 182
ثُمَّ نَادَى بِأَعْلَى صَوْتِهِ : الْجِهَادَ الْجِهَادَ عِبَادَ اللهِ! أَلاَ وَإِنِّي مُعَسْكِرٌ فِي يَوْمي هذَا، فَمَنْ أَرَادَ الرَّوَاحَ إِلَى اللهِ فَلْيَخْرُجْ.
Then Amīr al-mu’minīn shouted at the top of his voice : al jihād, al jihād (fighting, fighting), O creatures of Allāh ! By Allāh, I am mobilizing the army today. He who desires to proceed towards Allāh should come forward.