From the Heidelberg Catechism (1563):
What is your only comfort in life and in death?
ANSWER:That I am not my own, but belong—body and soul, in life and death—to my faithful Savior Jesus Christ. He has fully paid for all my sins with his precious blood, and has set me free from the tyranny of the devil. He also watches over me in such a way that not a hair can fall from my head without the will of my Father in heaven; in fact, all things must work together for my salvation. Because I belong to him, Christ, by his Holy Spirit, assures me of eternal life and makes me wholeheartedly willing and ready from now on to work for him.
What must you know to live and die in the joy of this comfort?
Three things: first, how great my sin and misery are; second, how I am set free from all my sins and misery; third, how I am to thank God for such a deliverance.