Is it obligatory to feed the poor on the same day that I fast to make up for missed days, or is it permissible to pay the full expiation and then fast?

Whoever delays making up for Ramadan without a valid excuse until another Ramadan overtakes him, then he must pay the Fidyah (feeding a poor person for each day). This is the view of the Malikis, Shafi'is, and Hanbalis, and it is the preponderant opinion based on the fatwa of Abu Hurairah and Ibn Abbas. It is permissible to give the Fidyah before making up the fast, as the general rule is that simultaneity is not a condition, even though some scholars preferred that it be given with or after the make-up fast.