Sound doctrine is God teaching us about himself, his ways and works, in his own words. And he tells us these things so that we will worship him alone.
Without sound doctrine we will think of God, ourselves and creation in the wrong way. And we will therefore relate to God and the things that he has made wrongly too.
The Bible, from beginning to end, calls us to confess the truth of God, and to confess it with our all.
Sound doctrine speaks, and sings, of the majesty, worth, glory and grace of the sovereign triune God. Saints love to tell of his ways and his works, of his wise decrees, mighty providence, awesome judgements and unfathomable grace.
Sound doctrine is truth to be believed, cherished, sung, proclaimed, taught, defended, remembered and passed on.
Have you ever wondered why God should tell us about those things that he planned before time? Of why he speaks to us of grace given to his people before the ages began? Is it not so that we would marvel at his ways, adore him, and worship Father, Son and Holy Spirit?
Is it important that we understand clearly the state of sin and misery that we are all in? How did we get there? How bad is it? What can be done about it?
If you are not from a church background where a "confession of faith" is a big deal in the week by week life of the church, or is thought of as perhaps a bit academic, the best place to start is with the these words:
1. What is your only comfort in life and in death?
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; indeed, 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 from now on to live unto Him.
2. How many things are necessary for you to know, that in this comfort you may live and die happily?
Three things: First, the greatness of my sin and misery. Second, how I am redeemed from all my sins and misery. Third, how I am to be thankful to God for such redemption.
You can read the rest here. Why not work through, and memorise, the first twenty one questions and answers of the Westminster Shorter Catechism? They set before us in clear, precise, and moving language the drama of the fall and the deliverance of a grace saved people out of the estate of sin and misery and into an estate of salvation, by a Redeemer.