What is Christian Liberty and Liberty of Conscience?
The liberty which Christ has purchased for believers under the Gospel consists of their freedom from the guilt of sin, the condemning wrath of God, and the severity and curse of the [moral] law. It also includes their deliverance from this present evil world, bondage to Satan, the dominion of sin, the distress of afflictions, the fear and sting of death, the victory of the grave, and everlasting damnation. Furthermore, it includes their free access to God, and their ability to yield obedience to Him, not out of slavish fear, but with childlike love, and willing minds.
All these blessings were also shared in essence by believers under the [Old Testament] law; but, under the New Testament, the liberty of Christians is further enlarged in their freedom from the yoke of the ceremonial law to which the Jews were subjected. We also have greater boldness of access to the throne of grace, and fuller provision of the free Spirit of God than believers under the law normally experienced.
God alone is Lord of the conscience, and He has left it free from [obligations to] human doctrines and commandments which are in any way contrary to His Word or not contained in it. So to believe such doctrines, or to obey such commandments out of conscience, is to betray true liberty of conscience. To require an implicit faith, or absolute and blind obedience, is to destroy liberty of conscience and reason.
Those who practice any sin or harbour any sinful desires on pretence of Christian liberty, pervert the main purpose of the grace of the Gospel to their own destruction. They completely destroy the purpose of Christian liberty, which is that we (having been delivered from all our [spiritual] enemies) might serve the Lord without fear, in holiness and righteousness before Him all the days of our lives.