Bekhorot 51: Rabbi Tarfon Gave Back the Money

2 mishnayot! 1 - Redemption of the first-born son has to be done via the 5 silver coins (not via objects or land or promissory notes). Rabbi Yehudah HaNasi says - Anything but promissory notes would work, which indicates that his view is not the view of the mishnah. 2 - If the father paid the coins at once, that fulfills the obligation, but what if he handed them over one by one, or to several kohanim? Or if the kohen takes the payment and then returns it? Note how wealthy Rabbi Tarfon didn't keep the coins.