פירוש על בבא מציעא 68:3

on Rashi the children paid: (Rashi points out) and the father did not have chance to say he will pay, before he died (till here is rashi)... (Rashi) needs to explain (the sequance of events) in this way, for if father had said he will pay (before his passing), it would be simpel that they son get the rights to double. except in a case where they clerly backtracked (on their fathers words) and said they will not pay... however (says the Penei Yehoshua) it is impossible to explain that the case is that the father passed away before it (the product) was stolen, for if so (that the father passed away before the time of the theft) the responsibility to safeguard the product has left (from the father-watchman) and the hairs have no obligation to pay (in a case of theft), and since they are exempt from payment, even in a case that they paid on their free will, they were not rewarded with the double.