“A Cistercian monk who was in purgatory, said to the Sacristan of his monastery, ‘Assist me, I beseech you, by your prayers, for of myself I can obtain nothing.’ — Istor. dell. Ord. Cist. This is conformable to the doctrine of St. Bonaventure: ‘The poverty,’ he says, ‘of a beggar renders him unable to pay his debts.’ S. Bona. Serm. de Morte. And such is the indigence of these suffering souls, that they have no means of making satisfaction to God’s justice.
It is of faith that we can assist them by our suffrages, and particularly by the prayers recommended and used by the church for their deliverance. For my part, I cannot conceive how a christian can be excused from sin, who makes no effort to relieve them, even by his prayers.”  St. Alphonsus de Liguori, A Short Treatise on Prayer