Devotion, in the language of ascetical writers, denotes a certain ardor of affection in the things of God, and even without any qualifying prefix it generally implies that this ardor is of a sensible character. On the other hand, by the term "devotions" in the plural, or "popular devotions", we commonly understand those external practices of piety by which the devotion of the faithful finds life and expression. The efficacy of these practices in eliciting feelings of devotion is derived from four principal sources, either:
•    by the strong appeal which they make to man's emotional instincts, or
•    by the simplicity of form which puts them within the reach of all, or
•    by the stimulus of association with many others in the same good work, or
•    by their derivation from the example of pious persons who are venerated for their holiness.

No doubt other reasons besides these might be found why this or that exercise brings with it a certain spiritual unction which stimulates and comforts the soul in the practice of virtue, but the points just mentioned are the most noteworthy, and in the more familiar of our popular devotions all these four influences will be found united.

Historically speaking, our best known devotions have nearly all originated from the imitation of some practice peculiar to the religious orders or to a specially privileged class, and consequently owe most of their vogue to the fourth of the influences just mentioned. The Rosary, for instance, is admitted by all to have been known in its earliest form as "Our Lady's Psalter". At a time when the recitation of the whole hundred and fifty Psalms was a practice inculcated upon the religious orders and upon persons of education, simpler folk, unable to read, or wanting the necessary leisure, recited instead of the Psalms a hundred and fifty Pater nosters or supplied their place more expeditiously still by a hundred and fifty Hail Marys said as salutations of Our Lady. The Rosary is thus a miniature Psalter. Again, at a time when the most ardent desires of Christendom centered in the Holy Land, and when lovers of the Crucified gladly faced all hardships in the attempt to visit the scenes of the Savior's Passion, those unable to accomplish such a journey strove to find an equivalent by following Christ's footsteps to Calvary at least in spirit. The exercise of the Stations of the Cross thus formed a miniature pilgrimage. Similarly, the wearing of a scapular or a girdle was a form of investiture for people living in the world, by which they might put on the livery of a particular religious institute; in other words, it was a miniature habit. Or again, those who coveted the merits attaching to the recitation of the day and night hours of the clergy and the monks supplied their place by various miniature Offices of devotion, of which the Little Office of the Blessed Virgin and the Hours of the Passion were the most familiar.
 

The History of the Chaplet of The Divine Mercy

In 1935, St. Faustina received a vision of an angel sent by God to chastise a certain city. She began to pray for mercy, but her prayers were powerless. Suddenly she saw the Holy Trinity and felt the power of Jesus’ grace within her. At the same time she found herself pleading with God for mercy with words she heard interiorly: 

Eternal Father, I offer You the Body and Blood, Soul and Divinity of Your dearly beloved Son, Our Lord Jesus Christ, in atonement for our sins and those of the whole world; for the sake of His sorrowful Passion, have mercy on us. (Diary, 475) 

As she continued saying this inspired prayer, the angel became helpless and could not carry out the deserved punishment (see 474). The next day, as she was entering the chapel, she again heard this interior voice, instructing her how to recite the prayer that our Lord later called "the Chaplet." This time, after "have mercy on us" were added the words "and on the whole world" (476). From then on, she recited this form of prayer almost constantly, offering it especially for the dying. 

In subsequent revelations, the Lord made it clear that the Chaplet was not just for her, but for the whole world. He also attached extraordinary promises to its recitation. 

Encourage souls to say the Chaplet which I have given you (1541). Whoever will recite it will receive great mercy at the hour of death (687). When they say this Chaplet in the presence of the dying, I will stand between My Father and the dying person, not as the just Judge but as the Merciful Savior (1541). Priests will recommend it to sinners as their last hope of salvation. Even if there were a sinner most hardened, if he were to recite this Chaplet only once, he would receive grace from My infinite mercy (687). I desire to grant unimaginable graces to those souls who trust in My mercy (687). Through the Chaplet you will obtain everything, if what you ask for is compatible with My will. (1731) 

Prayed on ordinary rosary beads, The Chaplet of The Divine Mercy is an intercessory prayer that extends the offering of the Eucharist, so it is especially appropriate to use it after having received Holy Communion at Holy Mass. It may be said at any time, but our Lord specifically told St. Faustina to recite it during the nine days before the Feast of Mercy (the first Sunday after Easter). He then added: "By this Novena, [of Chaplets] I will grant every possible grace to souls." (796) 

It is likewise appropriate to pray the Chaplet during the "Hour of Great Mercy" — three o'clock each afternoon (recalling the time of Christ’s death on the cross). In His revelations to St. Faustina, Our Lord asked for a special remembrance of His Passion at that hour. 
 

History of the Rosary

We cannot pinpoint how or when the rosary began as a popular devotion. The old tradition that it was personally delivered to St. Dominic by the Blessed Mother herself is now seriously questioned. On the other hand, the Dominicans certainly helped to standardize and popularize it throughout the 15th and 16th centuries. Pope Pius V, a Dominican, instituted the feast of Our Lady of the Rosary (now celebrated on October 7); he credited the efficacy of the rosary with the defeat of the Turks at the battle of Lepanto in 1571.

Around the year 1000, ordinary people began to recite 150 Our Fathers, divided into three sets of 50 and counted on strings of beads called paternosters. This became known as “the poor man’s Psalter” because they were copying the monks and nuns who recited the 150 psalms each day. As Marian devotion increased in the 12th century, the Carthusians and Cistercians helped develop and popularize a rosary of Hail Marys.

Historically, the rosary emerged from the instinct of ordinary Christians that they, too, were called to the practice of regular prayer and to sanctify their time and work throughout the day. They knew the monks and nuns were doing so with their recitation of the Divine Office of the Church. But the peasant people didn’t have the time to pause for choral reading. Their instinct was to insist on praying themselves. The rosary arose from the good sense of ordinary people that Baptism calls all to holiness of life, and this demands the regular practice of prayer.
 

The Rosary Today

What is the best way to say the rosary? The tradition is to meditate on the mystery of each decade rather than to focus on the words of each prayer. So, with the first Joyful mystery, the Annunciation, one can think about God’s great initiative here, about Mary’s openness to doing God’s will, and so on. Or, more contemplatively, one can imagine and enter into the setting as the Angel Gabriel appears to Mary, listen in to the exchange between them, and so on. The purpose of all such contemplation is to take the mystery into daily life to encourage Christian discipleship. As St. Pope John Paul II wisely commented, we have in the rosary “a treasure to be rediscovered.”