سورة الأنعام

Imam Baqir (peace be upon him): Allah never takes vengeance on a wrongdoer except by means of another wrongdoer, and this is the saying of Allah the Mighty and Majestic: وَ کَذَلِکَ نُوَلِّی بَعْضَ الظَّالِمِینَ بَعْضًا [And thus do We make some of the iniquitous to befriend others].

Imam Sadiq (peace be upon him): Allah has two punishments; one from the ruh (spirit) and the other is setting some people over others. What comes from the ruh is illness and poverty, and what comes from being set over is retribution, as Allah the Exalted has said: "And thus do We make some of the iniquitous to befriend others on account of what they earned" — of sins. So what is the sin of the ruh, from that comes illness and poverty, and what is from being set over is retribution. All of this, for the believer, is a punishment for him in this world and a chastisement for him in it. But for the disbeliever it is retribution upon him in this world and the evil chastisement in the hereafter. And this does not occur except through a sin, and sin comes from desire, and in the believer it is [in the form of] mistake, forgetfulness, being compelled, and what he cannot bear; and what is in the disbeliever is deliberateness, denial, transgression, and envy.

Ali ibn Ibrahim (may Allah have mercy on him): وَ کَذَلِکَ نُوَلِّی بَعْضَ الظَّالِمِینَ بَعْضًا بِمَا کَانُواْ یَکْسِبُونَ [And thus do We make some of the iniquitous to befriend others on account of what they earned]; whoever befriends their leaders [and follows and obeys them], We place them as their guardians. So on the Day of Resurrection they will be placed alongside them.