My wife's father and sister passed away. Is it possible that we sacrifice on behalf of them although they did not will, and if so, how should we do it?
Worships are for the alive. A person has no worship left related to him/her after death. The Glorified Allah commands:
“And that there is not for man except that for which he strives.” (An-Najm/ The Star 53:39)
“And whoever desires the Hereafter and exerts the effort for it in a believing manner, – it is those whose effort is ever appreciated [by Allah]. “ (Al-Isra/ The Night Journey 17:19)
As understood from these verses, worships are personal and performed by human’s own efforts. This goes on until the last breath of the person. In a verse the Glorified Allah commands:
“And worship your Lord until there comes to you the certainty (death). ” (Al-Hijr/ The Stones 15:99)
When a person dies, his/her Book of Deeds is closed, except for three types of people. Our Prophet (p.b.u.h.) explains this as follows:
“When a person dies, the opportunity of gaining more reward ends except for these three: a Sadaqa Jariyah (continuous charity), knowledge from which there is a benefit or a pious child who prays to Allah for him.” (Muslim, Vasiye, 4)
The only thing we can do for the deceased is invoking blessings upon them. The verses about this subject are below:
“Our Lord! Forgive me and my parents and the believers on the Day of Reckoning.” (Ibrahim/ Abraham 14:41)
“And those who came after them say: “Our Lord! Forgive us and our brothers who have preceded us in Faith, and put not in our hearts any hatred against those who have believed. Our Lord! You are indeed The Kind, The Merciful.” (Al-Hashr/ The Gathering 59:10)
As a result, it is not appropriate to sacrifice with the intention of bestowing its sawab to the deceased.