Here is Bach's St. Matthew Passion with Philipp Herreweghe directing the Kölner Philharmonie and Coro y Orquesta del Collegium Vocale Gent.
If Bach is known as first, it would be that he dedicated most of his music to the Lutheran Church. Bach was born after the Protestant Reformation, but he felt the influence of Martin Luther throughout his life, since Bach was at Luther's church for part of his life. Martin Luther had a profound influence on Bach's views of music, since Luther composed songs for the church in the German language and it was Luther that translated the Bible in the German language.
The St. Matthew Passion, based on the Gospel of St. Matthew, is about the suffering and death of Jesus Christ. This is not unusual as the church universal has celebrated the death of Jesus since its inception. The reason the church celebrates the death of Jesus is, of course, because it is through Jesus' personal and volitional sacrifice on the cross that the justice of God is satisfied. Thus, when a person puts their trust in Jesus Christ as Savior and Lord, it is His death that saves them from their sins to eternal life.
Bach undertook to compose this massive work in his time as the choirmaster to churches in Leipzig. The St. Matthew Passion was first heard in 1727 at the Good Friday afternoon service. The piece calls for two separate orchestras and choirs, which perform separately and together throughout the piece. One of the interesting aspects of the piece is that at certain points in the piece, Bach has moments of contemplation that is sung by soloists and the choirs.
Here is how David Gordon describes Bach's St. Matthew Passion: "The massive yet delicate work, with its multiple levels of theological and mystical symbolism, its powerful and dramatic biblical teachings, and its psychological insight, is one of the most challenging and ambitious musical compositions in the entire Western tradition."