What is the ruling regarding a person who accidentally caused the death of another, then confessed to the killing? Is he imprisoned, and for how long, knowing that the deceased had a dispute with my brother and the killer accidentally killed his companion?

The ruling on one who causes a killing varies depending on the nature of their causation:

1. If the causation was without knowledge or intent, such as someone who reports on a person without knowing they will be killed, then there is no blame on him. 2. If the causation was by ordering the killer or inciting him, the one who caused it is lashed one hundred times and imprisoned for one year, and he must repent and seek forgiveness. The direct killer is subject to qisas (retribution) unless the victim's guardians pardon him or accept diyah (blood money). 3. If the one who caused it colluded with the direct perpetrator, both are executed unless the victim's guardians pardon them or accept diyah. 'Umar ibn al-Khattab, may Allah be pleased with him, said: "If the people of San'a' had colluded in his killing, I would have killed them all." This is also the view of jurists, such as Khalil in Al-Mukhtasar.