Pope Saint John XXIII, with his apostolic letter “Inde a Primis” (June 30, 1960), explained its meaning and approved the litanies of the Precious Blood of Christ.
Benedict XVI said of this devotion:
The theme of blood linked to that of the Paschal Lamb is of primary importance in sacred Scripture. In the Old Testament the sprinkling of the blood of sacrificed animals represented and established the covenant between God and the people, as one reads in the Book of Exodus: “Then Moses took the blood and sprinkled it on the people saying: ‘This is the blood of the covenant that the Lord has made with you on the basis of all these words of his'” (Exodus 24:8).
Jesus explicitly repeats this formula at the Last Supper, when, offering the chalice to his disciples, he says: “This is my blood of the covenant, which will be shed on behalf of many for the forgiveness of sins” (Matthew 26:28). And, from the scourging, to the piercing of his side after his death on the cross, Christ has really shed all of his blood as the true Lamb immolated for universal redemption. The salvific value of his blood is expressively affirmed in many passages of the New Testament.
The blood of Christ is the pledge of the faithful love of God for humanity. Looking upon the wounds of the Crucified, every man, even in conditions of extreme moral misery, can say: God has not abandoned me, he loves me, he gave his life for me — and in this way rediscover hope. May the Virgin Mary, who beneath the Cross, together with the apostle John, witnessed the testament of Jesus’ Blood, help us to rediscover the inestimable riches of this grace, and to feel profound and perennial gratitude for it.
Several saints who had a devotion to the Precious Blood of Jesus, come to mind: St. Paul, St. Augustine, St John Chrysostom, St Gertrude, St. Catherine of Siena, Bl. Gaspar del Bufalo, Bl. Anne Catherine Emmerich,St. Veronica Giuliani,
The feast day of the Most Precious Blood of Jesus is July 1st.