A word implying 'debt', considered as a 'cause' but not as kartṛ or agent, takes the 5th case-affix.,
Ex. शताद्बद्धः 'he has been bound on account of a debt of a hundred pieces.'
Why do we say 'when not denoting the agent ?' Observe शतेन बन्धितः; 'a debt of hundred has thrown him in prison'; here शत being considered as a prayojaka hetu, is an agent and takes the third case-affix.,