Is it permissible to fast and give charity on behalf of the killing of a young child who died years ago, given that the killer has only one kidney, which prevents him from knowing his ability to fast?

The unlawful killing of a soul is divided into three categories: 1. Intentional killing (al-qatl al-ʿamd): When the killer intends to take a life using means that ordinarily cause death. 2. Semi-intentional killing (qatl shibh al-ʿamd): When the killer intentionally performs an act but does not intend to kill. 3. Accidental killing (qatl al-khaṭaʾ): When the injury occurs unintentionally, such as when one aims at something but accidentally hits a person, causing their death.

And whoever does not find a slave to free, then he must fast for two consecutive months.