From the earliest days of the Church, "Christ's open side and the mystery of blood and water were meditated upon, and the Church was beheld issuing from the side of Jesus, as Eve came forth from the side of Adam. It is in the eleventh and twelfth centuries that we find the first unmistakable indications of devotion to the Sacred Heart. Through the wound in the side, the wounded Heart was gradually reached, and the wound in the Heart symbolized the wound of love." (Catholic Encyclopedia)
General devotion to the Sacred Heart, the birthplace of the Church and the font of Love, were popular in Benedictine and Cistercian monasteries, especially in response to the devotion of St. Gertrude the Great (b. 1256), but specificdevotions became even more popularized when St. Margaret Mary Alacoque (1647-1690), a Visitation nun, had a personal revelation involving a series of visions of Christ as she prayed before the Blessed Sacrament. She wrote, "He disclosed to me the marvels of his Love and the inexplicable secrets of his Sacred Heart." Christ emphasized to her His love -- and His woundedness caused by Man's indifference to this love.
He promised that, in response to those who consecrate themselves and make reparations to His Sacred Heart:
- He will give them all the graces necessary in their state of life.
- He will establish peace in their homes.
- He will comfort them in all their afflictions.
- He will be their secure refuge during life, and above all, in death.
- He will bestow abundant blessings upon all their undertakings.
- Sinners will find in His Heart the source and infinite ocean of mercy.
- Lukewarm souls shall become fervent.
- Fervent souls shall quickly mount to high perfection.
- He will bless every place in which an image of His Heart is exposed and honored.
- He will give to priests the gift of touching the most hardened hearts.
- Those who shall promote this devotion shall have their names written in His Heart.
- In the excessive mercy of His Heart that His all-powerful love will grant to all those who receive Holy Communion on the First Fridays in nine consecutive months the grace of final perseverance; they shall not die in His disgrace, nor without receiving their sacraments. His divine Heart shall be their safe refuge in this last moment.
The devotions attached to these promises are:
- Receiving Communion frequently
- First Fridays: going to Confession and receiving the Eucharist on the first Friday of each month for nine consecutive months. Many parishes will offer public First Friday devotions; if they do, you must perform First Fridays publicly. If it isn't so offered in your parish, you can do this privately, going to Confession, receiving the Eucharist, and offering your prayers for the intention of the Holy Father.
- Holy Hour: Eucharistic Adoration for one hour on Thursdays ("Could you not watch one hour with me?"). Holy Hour can be made alone or as part of a group with formal prayers.
- Celebrating of the Feast of the Sacred Heart (see below)
Note also that June is devoted to the Sacred Heart.
Feast of the Sacred Heart
The Friday that follows the Second Sunday in Time After Pentecost is the Feast of the Sacred Heart which brings to mind all the attributes of His Divine Heart mentioned above. Many Catholics prepare for this Feast by beginning a Novena to the Sacred Heart on the Feast of Corpus Christi, which is the Thursday of the week before. On the Feast of the Sacred Heart itself, we can gain a plenary indulgence by making an Act of Reparation to the Sacred Heart.