Burying the deceased without washing him because his body is in pieces
Question

I am from Iraq. My cousin was killed by the occupying troops and sectarian gangsters. They kidnapped him, then they cut off his head with a knife, and they cut off his arms at the shoulders, then they left him on the ground for three days, and we were not able to go and collect his body because of the security situation, and the weather was very hot. Then someone came and covered him with soil. Then we were able to obtain the body, but it was decomposed, so I buried it, based on my own ijtihad (reasoning), without washing it, because we were not able to wash the body. Sometime later, I found out that I should have sprinkled water on it. Am I sinning because of that?
Praise be to Allah.We ask Allah to forgive your cousin, expiate his bad deeds, and admit him to Paradise by His mercy.
Washing the deceased (ghusl) is a communal obligation, according to scholarly consensus. It is one of the rights that one Muslim has over another.
‘Ala’ ad-Din as-Samarqandi said in Tuhfat al-Fuqaha’ (1/239):
Washing the deceased (ghusl) is obligatory according to the consensus of the ummah. End quote.
If the Muslims are able to wash their deceased, then it is obligatory for them to wash him, then shroud him, offer the funeral prayer for him, and bury him.
If they are not able to wash him because washing will cause the body to disintegrate further, they should pour water on him. If they are not able to do that either, they should do tayammum for him with dust. If they are able to wash some parts of his body or pour water over them, and not others, they should wash whatever they are able to, or pour water over it, and do tayammum for the rest of his body.
Ibn Qudamah (may Allah have mercy on him) said in al-Mughni (2/402):
In the case of one who was crushed beneath a falling wall, or burned, or drowned, if it is possible to wash him, he should be washed.
If there is the fear that washing may cause the body to disintegrate, then water should be poured over him and he should not be touched.
If pouring water over the body may cause it to disintegrate, he should not be washed. Rather tayammum should be done instead, if possible, as in the case of one who is living who will be harmed by water. If it is not possible to wash the deceased because no water is available, then tayammum should be done for him.
If it is not possible to wash part of him and it is possible to wash other parts, then that which can be washed should be washed, and tayammum should be done for the rest, exactly as in the case of one who is living. End quote.
See also the answer to question no. 154635 .
With regard to what we have mentioned above about doing ghusl or tayammum for the deceased, the time for that has passed in this case. If you did that because you were unaware of the shar‘i ruling, you do not have to do anything except seek forgiveness from Allah for hastening to act before asking, and you should realise that it is obligatory to seek out the shar‘i ruling regarding anything that you are faced with. Allah, may He be exalted, says (interpretation of the meaning):
{ So [O people] ask those who have knowledge, if you do not know } [al-Anbiya’ 21:7].
And Allah knows best.