When he received reports about those who had broken their oath of allegiance to him
ومن خطبة له (عليه السلام)
حين بلغه خبر الناكثين ببيعته
[وفيها يذم عملهم ويلزمهم دم عثمان ويتهدّدهم بالحرب]
Beware! Satan has certainly started instigating his forces and has collected his army in order that oppression may reach its extreme ends and wrong may come back to its position. By Allah they have not put a correct blame on me, nor have they done justice between me and themselves.

أَلاَ وإِنَّ الشَّيْطَانَ قَدْ ذَمَّرَ حِزْبَهُ وَاسْتَجْلَبَ جَلَبَهُ لِيَعُودَ الجَوْرُ إِلَى أَوْطَانِهِ، وَيَرْجِعَ البِاطِلُ إِلَى نِصَابِهِ وَاللهِ مَا أَنْكَرُوا عَلَيَّ مُنْكَراً، وَلاَ جَعَلُوا بَيْنِي وَبَيْنَهُمْ نَصِفاً
Criticism of their actions
يذم عملهم
They are demanding of me a right which they have abandoned, and a blood that they have themselves shed.1 If I were a partner with them in it then they too have their share of it. But if they did it without me they alone have to face the consequences. Their biggest argument (against me) is (really) against themselves.

They are suckling from a mother who is already dry, and bringing into life innovation that is already dead. How disappointing is this challenger (to battle)? Who is this challenger and for what is he being responded to? I am happy that the reasoning of Allah has been exhausted before them and He knows (all) about them.

وَإِنَّهُمْ لَيَطْلُبُونَ حَقّاً هُمْ تَرَكُوهُ، وَدَماً هُمْ سَفَكُوهُ، فَلَئِنْ كُنْتُ شَرِيكَهُمْ فِيهِ فَإِنَّ لَهُمْ لَنَصِيبَهُمْ مِنْهُ، وَلَئِنْ كَانُوا وَلُوهُ دُوني، فَمَا التَّبِعَةُ إِلاَّ عِنْدَهُمْ، وَإِنَّ أَعْظَمَ حُجَّتِهِمْ لَعَلَى أَنْفُسِهِمْ، يَرْتَضِعُونَ أُمّاً قَدْ فَطَمَتْ وَيُحْيُونَ بِدْعَةً قَدْأُمِيتَتْ. يا خَيْبَةَ الدَّاعِي! مَنْ دَعَا! وَإِلاَمَ أُجِيبَ! وَإِنِّي لَرَاضٍ بِحُجَّةِ اللهِ عَلَيْهِمْ وَعِلْمِهِ فِيهمْ.
The threat to wage war against them
التهديد بالحرب
If they refuse (to obey) I will offer them the edge of the sword which is enough a curer of wrong and supporter of Right.

It is strange they send me word to proceed to them for spear-fighting and to keep ready for fighting with swords. May the mourning women mourn over them. I have ever been so that I was never frightened by fighting nor threatened by clashing. I enjoy full certainty of belief from My God and have no doubt in my faith.

فَإِنْ أَبَوْا أَعْطَيْتُهُمْ حَدَّ السَّيْفِ، وَكَفَى بِهِ شَافِياً مِنَ البَاطِلِ، وَنَاصَراً لِلْحَقِّ! وَمِنَ العَجَبِ بَعْثُهُمْ إِلَيَّ أَنْ أَبْرُزَ لِلطِّعَانِ! وَأَنْ أصْبِرَ لِلْجِلادِ! هَبِلَتْهُمُ الهَبُولُ! لَقَدْ كُنْتُ وَمَا أُهَدَّدُ بِالحَرْبِ، وَلاَ أُرَهَّبُ بِالضَّرْبِ! وَإِنِّي لَعَلَى يَقِينٍ مِنْ رَبِّي، وَغَيْرِ شُبْهَةٍ مِنْ دِيني.