it depends. There is nothing in the nature of Sabbatical leave that would prevent a priest from saying Mass.
If the bishop choses to suspend his faculties, that is a different story.
Generally, Sabbatical leave is to give the priest a chance to rest, to engage in a different ministry for awhile, or to further his education. None of those are bars to saying Mass or hearing confessions.
Priest from other parts of the US come to DC region to study all the time. Some stay in residency at the local parishes and assist in cleebrating Mass and hearing confessions.
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