Exhorting people for jihad
ومن خطبة له (عليه السلام)
وهي كلمة جامعة له
فيها تسويغ قتال المخالف، والدعوة إلى طاعة الله، والترقي فيها لضمان الفوز
By my life there will be no regard for anyone nor slackening from me in fighting against one who opposes right or gropes in misguidance. O creatures of Allah, fear Allah and flee unto Allah from His wrath (seek protection in His Mercy). Tread on the path He has laid down for you and stand by what He has enjoined upon you. In that case `Ali would stand surety for your success (salvation) eventually even though you may not get it immediately (i.e. in this world).

وَلَعَمْرِي مَا عَلَيَّ مِنْ قِتَالِ مَنْ خَالَفَ الحَقَّ، وَخَابَطَ الغَيَّ مِنْ إِدْهَانٍ وَلاَ إِيهَانٍ فَاتَّقُوا اللهَ عِبَادَ اللهِ، وَفِرُّوا إِلَى اللهِ مِنَ اللهِ وَامْضُوا في الَّذِي نَهَجَهُ لَكُمْ، وَقُومُوا بِمَا عَصَبَهُ بِكُمْ فَعَلِيٌّ ضَامِنٌ لِفَلْجِكُمْ آجِلاً، إِنْ لَمْ تُمنَحُوهُ عَاجِلاً