Ordained a priest in 1846, Fr. Cavanagh began his priestly labors in the difficult years of the Great Famine, a time of hunger, disease and death in Ireland. His reputation for holiness took root in this time, when he did all in his power to feed the hungry, to visit the sick, and to minister to the dying. His parishioners saw him spending long hours in prayer both in the church and at his parish house.
In 1867 he was appointed parish priest of the combined parishes of Knock and Aghamore. There he became famous for his sermons, simple and direct, but profound and exacting in setting forth the truths of the Faith. He preached often on devotion to the Mother of God and constantly exhorted the faithful to pray for the Poor Souls in Purgatory.
He placed great emphasis on the importance of the Morning Offering, often instructing his flock to offer up all their thoughts, words, deeds and sufferings to the Sacred Heart of Jesus through the hands of Mary Most Holy. In this way they would sanctify their whole day and give glory to God by everything that they did.
Here are his words from a sermon on the Feast of Epiphany in 1882:
“Let each one of you never neglect the Sign of the Cross the moment you awake from sleep. Remember that there stands at your bedside, watching you, the Demon who wants to drag you down to Hell by tempting you to sin and the good Angel who watches you to help you to Heaven. You must choose for the day which you will follow. If you make the Sign of the Cross at once, you place yourselves on the side of God. You choose his standard, and the Devil will flee from you.
“When rising, you must praise and adore God for His goodness in sparing you to see another day. Never, never leave the room where you have slept – no matter what the hurry of your business may be – without saying at least three Our Fathers and Hail Marys in honor of the ever-Blessed Trinity, to place yourself under God’s protection for the day. This will take you only a few minutes.
“Then you must offer to God all your actions for the day that they may belong to Him! Oh! What merit you will have for any action thus offered to Him! It will not take you very long to say this short prayer:
I offer you all my thoughts words and action to the honor and glory of God, into the hands of the Blessed Virgin Mary, in union with the Adorable Heart of Jesus, and the sufferings of my Divine Lord for the Souls in Purgatory.
“All our actions are thus consecrated to God and offered to His honor and glory, and we leave all our actions at the disposal of the Blessed Virgin Mary for those holy souls who, when released from Purgatory, will never forget us. They will pray constantly for us at the throne of God. One soul released from Purgatory gives more glory to God than the entire universe.” (Liam Ua Cadain, Ven. Archdeacon Cavanagh: Pastor of Knock Shrine 1867-1897, Knock Shrine Society: 1955)
This was how Fr. Cavanaugh preached to his people, who always remained fully attentive and never seemed to grow tired – however long the address.
Following the Apparition on August 21, 1879, Fr. Cavanaugh was kept extremely busy with interviews and pilgrims’ confessions in addition to his own parish duties. In October 1879, he began keeping a diary of all cures reported at Knock. By the end of 1880, he had already recorded some 300. The Church investigated the Apparition of Knock at that time and again in 1936, and found nothing contrary to the faith in it.
Fr. Cavanaugh died on the Feast of the Immaculate Conception, December 8, 1897, and was laid to rest in Knock Parish Church.