If he does not know who he took the interest from, and he cannot determine which part of his wealth is lawful and which part is unlawful, then he should pay the khums from the mixed amount.
It is permissible to touch the dead, but if the body is cold and not given the ghusl then it is obligatory to perform ghusl of touching a dead body. The said ghusl is not required if the body was still warm or has been given the ghusl. Ghusl is not obligatory in all cases with the presence of a barrier between the hand and the deceased's body.
