Here is a relic of St. Dominic (i.e., the founder of the Dominican order). It is ex ossibus – i.e., a piece of one of his bones.
St. Dominic is usually associated with the spread of the rosary devotion. There is a popular legend that Our Lady appeared to him and entrusted him with the rosary; from there, he spread the devotion as he went about preaching against the Albigensian heresy. Some historians think this is a bunch of bunk. Well, if it’s not true, it should be.
Here is a painting by the famous painter Caravaggio on the subject:
Regardless of whether St. Dominic directly received the rosary from Our Lady, I’m pretty sure he’d instruct us to pray it. Pray the rosary! And St. Dominic, pray for us!