WASHINGTON — The incorrupt heart of St. John Vianney, the patron saint of parish priests, "reminds us God uses instruments to be ministers of his grace and mercy," said Archbishop Christophe Pierre, apostolic nuncio to the U.S.

He celebrated Mass Dec. 9 at the Basilica of the National Shrine of the Immaculate Conception in Washington that opened a four-day public veneration, which he prayed "would help people ask for the grace to change their lives."

A six-month tour will take the holy relic of the saint — popularly known as the Cure d'Ars — across the United States. Sponsored by the Knights of Columbus, the "Heart of a Priest" tour was launched in wake of the clergy sexual abuse crisis in the church.

Supreme Knight Carl Anderson, CEO of the Knights of Columbus, said in statement that St. John Vianney offers an example to help the church heal and rebuild.

"We now welcome as providential this opportunity to invoke the intercession of the patron saint of parish priests, whose holiness and integrity is a singular model for clergy," Anderson said in his statement.

St. John Vianney was born in 1786 and served as a simple parish priest in the French town of Ars. He was known to spend as many as 18 hours a day hearing confessions from people who traveled from throughout Europe to see the priest who was known for his holiness and piety. He also had a great love of and fostered devotion to St. Philomena. He died in 1859.

Pope Pius XI canonized him in 1925 and proclaimed him patron saint of parish priests in 1929. His incorrupt body and heart are displayed at his shrine in Ars.

With a trumpet fanfare and solemn procession, the holy relic was brought into the Crypt Church at the shrine and placed at the altar in front of an icon of the priest. It was on display through Dec. 12.

During the opening Mass, which drew 1,500 people, Archbishop Pierre called St. John Vianney "a man of faith." He noted the saint "was not a particularly handsome man. He did not have a beautiful voice, and it was well known that he was not very clever or good at studies ... but St. John Vianney had so much love. And, what did he offer the people? Forgiveness and mercy."

Veneration of the saint's heart "offers prophetic witness in a country that does not want to hear about forgiveness or mercy," Archbishop Pierre said. "He (St. John Vianney) was an authentic witness to those who seek a deeper union with God."

The church teaches that a relic — such as the heart of St. John Vianney — is offered to the faithful for veneration, but neither the relic nor the saint is worshipped. Veneration recognizes the fact that God has worked through the saint.

The nuncio also said that veneration of the saintly priest could lead to young men to consider a vocation to the priesthood.

"Perhaps there will be three men here — or maybe more — whom the Lord will raise up to be his faithful priests," he said.