By definition, an indulgence is the remission in whole or
in part of the temporal punishment due to personal sin,
provided that the sin has already been forgiven. The power
invested in the Church and her bishops and priests to grant
indulgences is found in several scriptures.
To Peter alone Jesus granted the first power to bind and
I will give you the keys to the kingdom of heaven.
Whatever you bind on earth shall be bound in heaven;
and whatever you loose on earth shall be loosed