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). Ruling 566.* The recommended precaution is that each of the three pieces of the kafan must not be so thin that the corpse can be seen through them.
However, if the pieces are such that all three of them together prevent the corpse from being seen, it will suffice.