You need both an inner Christ and an outer Christ. The outer Christ was the hallmark of the Reformation, when Martin Luther wrote that we need be Christ to one another. The inner Christ was the hallmark of the Great Awakening, when George Whitefield asserted the necessity of the new birth. Both are necessary to true Christianity; both are necessary for salvation; and both are biblical. Listen to the words of the apostle Paul.
Regarding the outer Christ, Paul wrote, “Put on the Lord Jesus Christ, and do not make provision for the flesh, to fulfill its lusts” (Romans 13:14). This verse was the great text that God used to save Augustine, who had been agonizing over his unwillingness to leave sexual sin for a life of purity in Christ. Technically, putting on Christ does not refer to conversion, but to the life of holiness that must follow true conversion. If we have truly heard Christ and been taught by Him, as the truth itself is in Jesus, we will put off the Old Man (Adam) and put on the New Man (Christ) (Ephesians 4:20-24). Christ Himself will be our wardrobe.
Even broader, if we are in Christ, having been immersed in Him through faith, the death-blows deserved by our sin have landed on His back. His death in our place has satisfied the demands of God’s Law for our punishment. We are justified in Him. Furthermore, His reward for obedience has become our unmerited reward, for we are carried in Him to the very right hand of God on high. We will be glorified in Him. Christ Himself has become our righteousness, and sanctification, and redemption (1 Corinthians 1:30). We are in Christ.
Regarding the inner Christ, Paul wrote once in exasperation, “My little children, of whom I travail in birth again until Christ be formed in you” (Galatians 4:19). Unless Christ is formed in us, we have no hope of heaven, for the same apostle testified elsewhere that “Christ in you” is “the hope of glory” (Colossians 1:27). If we do not have the Spirit of Christ–the Spirit who alone is the internal source of “love, joy, peace, patience, gentleness, goodness, faithfulness, meekness, temperance” (Galatians 5:22-23), that is, the source of spiritual life–if we do not have this Spirit dwelling within us, then we are not His, and He is not ours (Romans 8:9). Christ must be in us.
Let me ask you two questions from Puritan William Guthrie, whose book The Christian’s Great Interest sought to answer questions about personal salvation:
What has Christ done for you?
What has Christ done in you?
Do you have the outer Christ–the Christ of the Cross and the exaltation, the Christ of personal holiness that others can see and feel as fellow members of His church? Do you have the inner Christ–the Christ of the New Birth, the Christ of the renewed mind and heart by the Holy Spirit of God? These questions bring the whole matter of salvation down to the point of a pin: Do you have Christ? You must be in Him, and He must be in you. It is really that simple. With truth, the apostle John wrote, “This is the record, that God has given to us eternal life, and this life is in His Son. He who has the Son has life; and he who does not have the Son does not have life. These things I have written to you who believe on the name of the Son of God, that you may know that you have eternal life” (1 John 5:11-13).