Jesus taught that what’s in you will come out. Actually, he put it this way,
A good man produces good out of the good storeroom of his heart. An evil man produces evil out of the evil storeroom, for his mouth speaks from the overflow of the heart. Luke 6.45
This inescapable fact is what prompted Nicodemus to ask Jesus, “How can anyone be born when he is old?” (John 3.4) Nicodemus was keenly aware that no one could be something he is not simply by willing it. Jesus’ reply communicates clearly Jonah 2.9 that “salvation is of the LORD.” That is, one must be born again in order to become something that he is not. With men this is impossible; but with God—the God who created everything out of nothing in the first place—all things are possible (Matt 19.26), including rebirthing his own image bearers or, one might say, resurrecting them from the dead.
So, if death is “in” someone, only death can come out. Humanity’s default setting, ever since Adam, has been death. Paul told the Ephesian Christians that humanity apart from Jesus Christ is “dead in trespasses and sins” (Eph 2.1). So, really, only death could come out of us. One has suggested that even sinners’ so-called good deeds are no more than “splendid vices.” Sure, sinners work and marry and raise children and play and smile and do any number of good things God permits by his common grace. He does, after all, “cause his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous” (Matt 5.45). As missionary poet C. T. Studd has rightly mused, however, “Only one life, ’twill soon be past; only what’s done for Christ will last.”
If—on the other hand—life is “in” someone, then life is what will come out. When God originally created the being that would bear His image, He “blessed” him, not only commanding but also decreeing that he would be fruitful and multiply and fill the earth and subdue it (Gen 1.28). Inherent in God’s blessing—when and wherever it is granted—is provision of the fruitful flourishing of life. This life as its Creator intended it can come only from that Creator, who possesses life in himself (John 5.26); it can’t be acquired. Only those who are born again are granted renewed access to this tree of life. Now, life can dwell and flourish in them as they “live on every word that comes from the mouth of the Lord” (Deut 8.3). For this very reason, God charges believers to let the word of Christ dwell among them richly (Col 3.16). Then, what’s in them will come out.