A yearly retreat is required by canon law and imitates Jesus' own example of prayer before public ministry.
Canon law is very clear in its requirements of a yearly retreat for priests, religious and even seminarians.
“[Religious] are faithfully to observe the period of annual retreat” (Can. 663 §5).
“[Priests] are equally bound to make time for spiritual retreats according to the prescripts of particular law” (Can. 276 §2).
“Each year [seminarians] are to make a spiritual retreat” (Can. 246 §5).
Why is that?
If a priest takes time away from his parish, isn’t he abandoning his flock?
Jesus himself spent much time away from his flock, even making a spiritual retreat for 40 days before his public ministry.
Filled with the holy Spirit, Jesus returned from the Jordan and was led by the Spirit into the desert for forty days.Luke 4:1-3
Jesus repeatedly took time away from his ministry to pray in solitude, giving us an example to follow.
Dom Jean-Baptiste Chautard in The Soul of the Apostolate illustrates this principle with a powerful image.
If you are wise, you will be reservoirs and not channels … The channels let the water flow away, and do not retain a drop. But the reservoir is first filled, and then, without emptying itself, pours out its overflow, which is ever renewed over the fields which it waters.
Chautard firmly believed that in order for priests (or anyone else, for that matter) can give themselves to others, they must first be filled.
Otherwise, priests and religious risk becoming channels and burning out, with no water for themselves.
Retreats are important. and our spiritual leaders need to make time for themselves to be recharged.
This requirement for priests is also a signal for us in the laity. We also need to recharge our spiritual batteries, especially if we are parents. Without time for solitude and prayer, we risk not only our own soul, but the souls of those we care for.