Authentic Christian living requires mind and heart to work together in obedience to the Holy Spirit. Without knowledge of what the Lord wants from us, we cannot serve Him rightly. At the same time, all the knowledge in the world is insufficient to make us lead a life that glorifies God. If we have no love for the Creator and His law, then we cannot forsake all other gods but Him (Ex. 20:3; 1 John 5:21). Whatever we love more than the Lord and His will becomes, essentially, our god.
Ephesians 1–3, in a sense, focuses on the heart aspects of the Christian life. To be sure, these chapters present objective content that we must know and believe for salvation. Still, this content describes the horrible predicament from which we have been saved, and it presents our glorious destiny as one unified and sanctified people. This cannot help but make our hearts leap with joy. Recalling what our Savior has done, we grow in our affection for Him, becoming increasingly eager to do His will. Thus, we take off sin and put on Jesus willingly (4:17–24).
Yet the command to put on Jesus is a bit abstract, and we are left with this question: What does it mean to clothe ourselves in Christ in terms of practical, everyday living? Paul answers this question in the latter part of Ephesians 4, explaining, in a manner that our minds can easily grasp, how those who have put on Christ must live. Verse 25, for example, tells the Christian to “speak the truth with his neighbor, for we are members one of another.” The apostle emphasizes truth-telling here, especially within the church. Lying to others, particularly fellow believers, is not an option for the Christian. We are members of one another, and lies weaken the unity of Christ’s body, sowing seeds of division, discord, and distrust.
A propensity to lie is a particularly clear indication that we are refusing to put on Christ. “All mankind are liars” (Ps. 116:11) because those who are in Adam hate the truth. They prefer to twist facts to advance themselves, tear down other people, excuse their failings, and even avoid needed confrontations that can break the peace between friends and family. In Adam we are liars, hiding our sin and the sins of others to maintain a veneer of peace. But we are in Christ — who is truth Himself (John 14:6) — and so truth must be our highest goal.