Also known as the Forty Hours’ Prayer, Forty Hours’ Adoration, Quarant’ Ore, or Quarantore, the devotion consists in a solemn exposition of the Blessed Sacrament during 40 hours, continual according to the (), in honour of the 40 hours during which the Body of Our Lord is considered to have rested in the tomb. In countries where the nocturnal exposition is not feasible the exposition is held on three consecutive days.
The indulgences of the devotion were at first limited to the exact ritual observance of the devotions, but by decree of Pope Saint Pius X, in 1914, the indulgences may all be gained even when the devotion is interrupted, as is the custom in the United States. A plenary indulgence is granted to all persons who, being truly contrite and having received the Sacraments of Penance and the Eucharist, visit a church in which the exposition is held on one of the three days and pray there for the intentions of the Holy Father.
Introduced by Saint Anthony Mary Zaccaria in Milan and Vicenza, Italy in 1527, it was spread to many places in Italy by the Capuchin, Joseph of Fermo, and was introduced into Rome and Germany by Jesuits under Saint Ignatius of Loyola. The devotions were approved by Pope Paul III in 1539, though some say Pope Clement VII in 1534. The , the right form for this devotion, were given out at Rome in 1705 by Pope Clement IX. At first the instructions were only for Rome itself, but at a later period were extended to the entire world.
The introduction into America is disputed. The first to hold these devotions with any degree of regularity was Saint John Nepomucene Neumann when bishop of Philadelphia. In 1857 Archbishop Patrick Francis Kenrick obtained from Pope Blessed Pius IX the modifications which are in use in the United States.