The text snippet discusses the book of Philippians, which is a letter written by Paul to the church at Philippi. Paul begins the letter with a prayer of thanksgiving and expresses his gratitude for the church. He also thanks them for their gift and encourages them to live in a way that promotes the Gospel, demonstrates unity, and trusts in God. The main theme of the book is joy, and Paul writes from prison. He addresses the saints, overseers, and deacons, and urges them to persevere for the sake of the gospel. The purpose of his letter is to encourage and exhort the Philippians to stand fast in unity and worship God through Jesus Christ. This book is considered a canonical letter that expresses the joy and encouragement in following Christ despite difficulties and challenges.