Paul Brand, the hand surgeon renowned for his discoveries in leprosy and his vibrant Christian faith, wrote often about the parallels between the church as the Body of Christ and the human body. The metaphor Jesus used in John 15 about the relationship between Him and His people, that of a vine, is another powerful illustration of the intimate, dependent, and fruitful relationship we have with Christ our Creator and Sustainer.
As each organ, liver, brain, kidneys, and heart, is an integral part of the human body, so the branch is an integral part of the vine and each man an integral part of the body of Christ. More precisely, as each human cell is vital to the life of man so each plant cell is to the life of the vine and each believer is to the body of our Lord. To abide in Christ is, therefore, analogous to the relationship between a cell and the body and a branch and its vine.
The human cell receives its nutrition from the rest of the body, specifically from groups of cells and organs which interdependently provide nutrients to the entire body. The plant cell receives its sustenance in the same way. Christians receive nutrition, both physical and spiritual, ultimately from the Lord, who is the Creator and Sustainer of all things. However, we receive them through complex interdependent systems which include farmers and grocers for our physical nourishment and pastors and teachers for our spiritual nourishment. No one separated from Christ and outside the systems He has designed can receive the nutrition he needs to survive. To abide in Christ means to be in intimate relationship with Him and with other believers also in close relationship with the Lord, because without such connections we will starve spiritually.
The human cell has intricate structure but by itself has little resistance to outside forces. The plant cell, with its thick cell wall, has more, but still is weak compared to the pressures of the environment. Only in association with other cells such as those that form human skin and human bone and other substances such as keratin and fibrocartilage can each individual human cell withstand the forces around it. The plant cell likewise can only survive within the structure of other cells in the plant. To abide in Christ, therefore, means to be in community with Him and other Christians, protecting one another and supporting one another to prevail against physical hardship and the forces of the Evil One. No Christian can stand alone and to think that we can is the pinnacle of pride.
In an environment in which a human cell has the nutrition and the protection it needs, that cell is free to do the work intended by its Creator. The human body, comprised of millions of cells, exists to worship and enjoy God and benefit others. In an environment in which a plant cell, such as a vine, has the nutrition and protection it needs, that cell is free to work with other cells and produce fruit. This fruit blesses other plants, animals and man in its environment. Those who abide in Christ have their basic needs met and therefore are able to, and are expected to, produce fruit to benefit others. This includes worshipping God, the source of the vine, and helping others.
To abide in Christ means to be in Christ as a cell is in a human body or in a vine, absolutely dependent on Him (and on others through the system He has designed), for sustenance and protection. It also means to bear fruit for the glory of God and the benefit of others in the body in which He has placed us.
The system is not static. The human body and the vine both constantly adjust to changes in the environment and stresses to themselves. Our God allows our environment to change and stresses to affect us as He shapes us into the people He wants us to be.
Practically speaking, to abide in Him requires that we think His thoughts, understand His work, both in Creation (general revelation) and in His word (special revelation), and do His acts. As Christ let His mind dwell on the Father, as Christ knew the Father intimately and as He did the works of the Father (John 14:10), so those of us who abide in Him must do the same.