God's life within us is likened to seed in I Peter 1:23: ". . . having been born again, not of corruptible seed but incorruptible . . ." Jesus also speaks of being born again or born from above (John 3:3-8) by the Spirit. The incorruptible seed is the Holy Spirit birthing us into God's family. John 1:12-13 says, "As many as received Him (Jesus, the Word of God), to them He gave the right to become children of God, to those who believe in His name; who were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God."
Do you see the correlation between those two verses? When we are born into God's family, we are not birthed by any human means—i.e. "corruptible seed"—rather, we are born of God, "of incorruptible seed." This is rich metaphor.
When an ovum, a woman's egg, is fertilized by the sperm, a child is born—not born into this world yet, but birthed within the mother. Through no human effort, that child begins to miraculously develop. It requires no to-do list on the part of the mother. Once that egg is fertilized, it will grow. In the Bible sperm is referred to as seed.
God created this process to teach us spiritual truth. Our spiritual life is birthed by the Holy Spirit of God. We are "born of God," of "incorruptible seed." Whether we think of the conception of a child or of seeds sprouting from dark hidden places under the earth, the life is in the seed. Life springs forth; the child, or the plant, grows, developing into full maturity because Life is in the seed. When the Holy Spirit connects with our spirit, Life germinates within us. God's eternal nature begins to manifest itself.
In order for that Life to burst forth, there must be the right conditions, to be sure. Flower or vegetable seeds don't grow while they are lying dormant in the packet. They must be put into the ground and watered, fertilized, and weeded. The conception of a child also requires the right conditions and the right timing. Once conceived, proper nourishment and rest help the child within to grow strong and healthy. In these types of ways we can nurture the life of the Spirit within us.
We cannot create life or cause growth, but we can help maintain the right conditions for that miracle of life to flourish. By cultivating our heart (Hosea 10:12, Jeremiah 4:3), we allow the Holy Spirit within our spirit to have greater and greater access to and influence over our soul—our mind, our will, and our emotions. The more the Holy Spirit controls our soul, which in turn controls our body, the more we become sanctified through and through, set apart for God in every aspect of life.
As we grow in Christ by the power of the Holy Spirit within us, our inner nature takes on the character and likeness of God, just as a newborn baby manifests a likeness to his or her parents. As the child grows and matures, friends and relatives see more and more characteristics of the parents. Not only are physical features dominant, but also mannerisms and vocal inflection, even likes and dislikes and personality idiosyncrasies.
These likenesses are derived from two main sources: internal DNA and close proximity or environmental relationship. We look and act like our parents because we carry their DNA; we share a composite blend of who they are. We learn mannerisms because we live with them day in and day out; we have learned from them their ways.
So it is with our sanctification. We take on the spiritual characteristics of God because His spiritual DNA has been implanted in us. His life cannot help but manifest itself in us. After we are "born again," we become uncomfortable with sin and are convicted of things that before we did without a pang of conscience. That is proof of God's holy Life within us!
But we also take on more of God's character, His mannerisms, so to speak, as we spend more time with Him. By cultivating a conscious sense of His ever-present-ness, we learn to ask Him about decisions, big and small; we follow His Word and His leading in how to respond to situations and relationships; we check our thoughts, attitudes, and actions, measuring them by the instruction of His Word and by the life of Christ. We seek to know and learn His character through time alone with Him in prayer and in His Word. There's no substitute for time spent with God.
The more time we spend with God and the more we cultivate an awareness of the reality of His presence within us, the more we will bear His likeness, which is God's intended goal as Romans 8:29 tells us: that we would be conformed to the image of His Son. This is both the meaning and the purpose of sanctification.