As you pray the Rosary, this guide allows you to insert a word or phrase after the name “Jesus” to curb distractions and to refocus attention to the mystery considered. Pope Saint John Paul II, in his Apostolic Letter on the Rosary (Rosarium Virginis Mariae), writes:
Pope Paul VI drew attention, in his Apostolic Exhortation Marialis Cultus, to the custom in certain regions of highlighting the name of Christ by the addition of a clause referring to the mystery being contemplated. This is a praiseworthy custom, especially during public recitation. It gives forceful expression to our faith in Christ, directed to the different moments of the Redeemer’s life. It is at once a profession of faith and an aid in concentrating our meditation, since it facilitates the process of assimilation to the mystery of Christ inherent in the repetition of the Hail Mary (RVM 33).
Additional Clauses for Help to Meditate upon the Mysteries of the Rosary – KATERI TEKAKWITHA
The “Mystery-Clauses”: Uniting Verbal and Mental Prayer in the Rosary | Tom’s Digest (wordpress.com)