The Sacred Heart of Jesus is one of the three solemnities of Ordinary Time and is celebrated on the second Friday, after the Solemnity of Corpus Christi.

The origin of this devotion is due to Saint Margaret Mary of Alacoque, a Sister of the Order of the Visitation of Saint Mary,  a religious order founded by Saint Francis de Sales and Joan Frances de Chantal, in 1610. Saint Margaret Mary had extraordinary revelations from Jesus, who personally commissioned her to announce and expand this pious devotion throughout the world. There were 3 apparitions of Jesus: The first took place on December 27, 1673, the second in 1674 and the third in 1675. Later, another nun, Blessed Mary of the Divine Heart, Countess of Droste zu Vischering, starting from Portugal, extended this devotion to the whole world through an act of solemn consecration requested from Pope Leo XIII.

Jesus left 12 great promises to the people who participate in the reparatory communions of the first Fridays. He said: "I promise you, by My immense mercy and the almighty love of My Heart, to grant to all those who receive Communion on the first Fridays of 9 consecutive months, the grace of final penance; they will not die in My enmity, not even without receiving the sacraments and My Divine Heart will be a safe refuge for them in this last hour."

There are many saints and popes who, over time, on various occasions, have recommended this devotion to the Heart of Jesus.