The Three Forms of Unity is the collective name for The Belgic Confession of Faith, The Heidelberg Catechism, and The Canons of Dort. These confessional statements summarize Calvinistic doctrine of faith and are accepted official statements of biblical teaching in Reformed churches throughout the world.
Collectively, these documents contain the fullness of the gospel and are masterful expressions of a beautiful message that is deeply moving, theologically concise, and scripturally sound. One would be hard pressed to find a more richly satisfying explanation than in Question and Answer 1 of The Heidelberg Catechism:
Question 1: What is thy only comfort in life and death?
Answer: That I, with body and soul, both in life and in death, am not my own, but belong to my faithful Savior Jesus Christ, who, with His precious blood, has fully satisfied for all my sins, and redeemed me from all the power of the devil; and so preserves me, that without the will of my Father in heaven not a hair can fall from my head; yea, that all things must work together for my salvation. Wherefore, by His Holy Spirit, He also assures me of eternal life, and makes me heartily willing and ready henceforth to live unto Him.