Mitzvah Shopping (Yoma 33a and 57a)

The Radvaz was once asked whether a prisoner who was given a one-day furlough each year should take it at the earliest opportunity or wait for Yom Kippur. After all, on Yom Kippur one can perform more important mitzvot. Based on the precept of ein maavirim al hamitzvot, he ruled that the prisoner should take it now even though it was an ordinary weekday. The Chacham Zvi disagreed. If you can be certain, he says, that the authorities will not change their minds, it is preferable to wait for Yom Kippur.