First Friday Hour of Reparation

Nine consecutive First Fridays in reparation to the Sacred Heart of Jesus
Our Lord appeared to St. Margaret Mary Alocoque (1647-1690), a French nun in the Visitation Order, and gave her the special task to spread devotion to His Most Sacred Heart at a time when religion was growing cold in the hearts of mankind.
He said to her:
“Behold this heart which, not withstanding the burning love for men with which it is consumed and exhausted, meets with no other return from most Christians than sacrilege, contempt, indifference and ingratitude, even in the sacrament of my love [the Eucharist]. But what pierces my heart most deeply is that I am subjected to these insults by persons especially consecrated to my service.”
Jesus asked for special prayers and practices to make amends (reparation) for this great neglect to the proper reverence owed to God. For those who did this faithfully, he made what St. Margaret Mary referred to as the “Great Promise” which was the last and greatest of the Twelve Promises of the Sacred Heart of Jesus.
“I promise you in the unfath­omable mercy of my heart that my omnipotent love will procure the grace of final penitence for all those who receive communion on nine successive first Fridays of the month; they will not die in my disfavor [the grace of final repentance], or without having received the sacraments, since my divine heart will be their sure refuge in the last moments of their life.”
Read more here
https://www.catholiccompany.com/getfed/what-is-the-first-friday-and-first-saturday-devotion/