Imam Sadiq (a.s.) was asked regarding the verse – وَ مَنْ قُتِلَ مَظْلُوماً فَقَدْ جَعَلْنا لِوَلِيِّهِ سُلْطاناً فَلا يُسْرِفْ فِي الْقَتْلِ إِنَّهُ كانَ مَنْصُوراً

‘and whoever is slain unjustly, We have indeed given to his heir authority, so let him not exceed the just limits in slaying; surely he is aided.’ (Surah Bani Israel (17): 33)

Imam Sadiq (a.s.) – It is revealed concerning Imam Husain (a.s.) – if his successor slays the entire population of the earth as vengeance for Imam Husain’s (a.s.) killing, it will not be extravagant and his successor is the Qaim (a.s.).
Al-Burhaan fi Tafseer al-Quran v 3 p 530