St. Josaphat was a monk of the Order of St. Basil, and afterward Archbishop of Polotsk, in Poland. His labors for the union of the Ruthenian Church with that of Rome were almost incredible. After a youth of singular innocence mortified by voluntary penance, Josaphat, remembering the powerful support lent to the orthodox cause by the monastic orders, entered religion and with the help of Velamin Rutski, devoted himself to the restoration of the rule of St. Basil.
As Superior of a monastery the saint had succeeded in keeping his disciples free from any schismatic taint: so, too, as metropolitan he devoted himself to the conquest of error with ardent and enlightened charity. He gave to all the example of a holy life, and labored for souls by preaching, by teaching the catechism, and by the distribution of controversial works. As a result of his zeal many schismatics were reconciled to the Catholic Church. His opponents at last resolved to take his life, and he suffered martyrdom at their hands with great courage and serenity at the age of 43.
In 1642, Urban VIII placed his name in the ranks of the Blessed, and Pius IX, on June 29, 1867, on the occasion of the centenary of the Princes of the Apostles, canonized the zealous champion of the Primary of the Roman Church. The Ruthenians celebrate his feast on September 16.
(Source: The New Roman Missal, Rev. F. X. Lasance)