Purity: When the Deceased Has No Estate
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 565:
If a deceased person does not have an estate from which his kafan can be purchased, it is not permitted to bury him naked; rather, based on an obligatory precaution, it is obligatory for the Muslims [who come to know about this] to shroud him. It is permitted to pay for the kafan from alms tax (zakat).
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)