Abu Imran al-Jawni said: I said to Sayyiduna Jundab (may Allah be pleased with him): Sayyiduna Ibn al-Zubayr (may Allah be pleased with him) took my pledge that I would fight whoever fights him, and now he is calling me to fight the people of Syria. He said: Pay a ransom (to be excused). I said: They have refused, saying that nothing will do except that I fight alongside them. He said: A man told me, and by Allah he did not lie to me, that the Prophet (peace and blessings be upon him) said: "On the Day of Resurrection a servant will come holding another man by the hand and will say: O Allah, this man killed me. Allah Almighty will ask: Why? He will say: So that the kingship of so-and-so might be established."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16803