Scripture derives some principle of conduct from every gift of God described to us in it, and from every aspect of our salvation. God has manifested Himself as Father to us. If we do not manifest ourselves as sons to Him in turn, we prove ourselves to be extremely ungrateful (Mal. 1:6; 1 John 3:1).
Therefore be imitators of God, as beloved children. (Eph. 5:1)
Christ has cleansed us by washing us with His blood, and has communicated this cleansing to us through baptism. It would be inappropriate, therefore, for us to defile ourselves with fresh filthiness (1 Cor. 6:11; Eph. 5:26; Heb. 10:10; 1 Peter 1:15, 19). Christ has engrafted us into His body. We, therefore, who are His members must be especially careful not to fling mud or filthiness on the body of Christ (John 15:3–6; 1 Cor. 6:15; Eph. 5:23–33). Christ our Head has ascended into heaven. We, therefore, must set aside earthly affections and wholeheartedly long for that place (Col. 3:1ff.). The Holy Spirit has consecrated us as temples of God. We, therefore, must let the glory of God shine through us, and we must not pollute ourselves with sin. Our bodies and souls have been destined to heavenly incorruption and an unfading crown. We, therefore, must strive upward—keeping ourselves pure and incorruptible until the Day of the Lord (1 Thess. 5:23). These are most holy foundations on which to build the Christian life. Nothing like these can be found in the philosophers, who in their commendation of virtue never rise above the dignity that natural man can achieve.
Something must be said about those who want to be called Christians but possess nothing of Christ except the title and appearance. They arrogantly glory in His holy name. But only those who have gained a true knowledge of Christ from the Word of the gospel have a relationship with Him. And the Apostle denies that any have rightly learned Christ who have not learned that they must put off the old man, who is corrupted by deceitful desires, and put on Christ.
But that is not the way you learned Christ!—assuming that you have heard about him and were taught in him, as the truth is in Jesus, to put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires, and to be renewed in the spirit of your minds, and to put on the new self, created after the likeness of God in true righteousness and holiness. (Eph. 4:20–24)
Such nominal Christians demonstrate their knowledge of Christ to be false and offensive no matter how eloquently and loudly they talk about the gospel. For true doctrine is not a matter of the tongue, but of life; neither is Christian doctrine grasped only by the intellect and memory, as truth is grasped in other fields of study. Rather, doctrine is rightly received when it takes possession of the entire soul and finds a dwelling place and shelter in the most intimate affections of the heart. So let such people stop lying, or let them prove themselves worthy disciples of Christ, their teacher.
We have given priority to doctrine, which contains our religion, since it establishes our salvation. But in order for doctrine to be fruitful to us, it must overflow into our hearts, spread into our daily routines, and truly transform us within. Even the philosophers rage against and reject those who profess an art that ought to govern one’s life, but who twist that art hypocritically into empty chatter. How much more then should we detest the foolish talk of those who give lip service to the gospel? The gospel’s power ought to penetrate the innermost affections of the heart, sink down into the soul, and inspire the whole man a hundred times more than the lifeless teachings of the philosophers.
John Calvin, A Little Book on the Christian Life, trans. and eds. Aaron Clay Denlinger and Burk Parsons (Orlando, Fla.: Reformation Trust), 2–13.