It is common knowledge that for centuries, the Catholic Church conducted mass in Latin. That changed in the 1960s, when after the Second Vatican Council, mass  was conducted in the vernacular. The religious use of Latin has contributed much to the history of the language. 

The early Christian writer, Tertullian (160 A.D. - 220 A.D.) is considered the founder of Latin language Christianity. Previously, many of the religious writings were written in Greek. Works by Tertullian include Ad Martyras (to the martyrs) and the two letters written to his wife (Ad Uxorem, 1 and 2). 

The Latin Vulgate is a translation of the Bible into Latin in 382 A.D., by St. Jerome (342 A.D. - 420 A.D.) who was commisioned in 382 A.D. by Pope Damasus to revise the Gospels then in use by the Catholic Church, and he extended his work to include most of the Bible. 

Polish hymn, Bogurodzica (Mother of God), is the oldest Polish hymn, and dates back to the 10th - 13th century.

The oldest known prose in the Polish language is Kazania świętokrzyskie, the Holy Cross Sermons, date from the late 13th or early 14th century and were originally housed at the Holy Cross Monastery, which they were named after.

The part that Latin has played in religious history is very significant. Here are some Latin religious terms:

Absit - God forbid

Adeste fideles - come faithful

Agnus Dei - Lamb of God

Ave Maria - Hail Mary

Corpus Christi - Body of Christ

Filius Dei - Son of God

Mea culpa - my fault

Gloria in Excelsis Deo - Glory to God in the Highest

Pacem in terris - Peace on Earth

Ave verum corpus is a hymn from the 14th century that has been set to music by various composers including Mozart.  the  Latin text and Englih translation is as follows:

Many old traditional hymns were originally written in Latin.  

A hymn whose words were attributed to Pope Gregory the Great (Pope from 590 - 604) mentions the observance of the season of Lent. During the Middle Ages, this included fasting, and people were expected to give up meat, cheese, dairy products and eggs for the 40 days of Lent (leading up to Easter). 

 O sanctissima is a hymn, first published in 1792 and since then has become closely associated with Christmas. Some of the words are Mater amata intemerara, ora, ora pro nobis (Beloved Mother, undefiled, pray, pray for us).

One web site with hymns in Latin, English and sound files of the melodies can be found at:

http://fisheaters.com/hymns.html

Saint Nicetas (335 - 414) was Bishop of Remenane (located in modern day Seribia. He promoted the use of Latin language sacred music in the worship service and was said to have compossed a number of hymns.  The Christian hymn Te Deum, is generally attibuted to St. Ambrose and St. Augustine.