When a new graft is placed on a vine and it remains there, a twofold process takes place. In the first, the graft shoots its roots and fibers down into the stem, and the stem grows up and into the graft. A structural union is then produced. The graft becomes one with the vine. Even if the vine dies it would still be one with it. In the second process the sap of the vine enters into the new structure, using it as a passage way through which sap can flow up to show itself in young shoots, leaves, and fruit. Here is the vital union. Into the graft that remains in the stock, the stock enters with sap to live in it.
When Christ said, "Abide in Me, and I in you," He points out something which is as the grafting process in nature. "Abide in Me" refers more to what we have to do. We have to trust and obey, to detach ourselves totally and completely from all else, to reach out after Him and cling to Him, to sink ourselves into Him.
More than a few believers pray and fervently desire the filling of the Spirit and the indwelling of Christ. They wonder why it is they make no progress. Often the reason is this: the "I in you" cannot come because the "Abide in Me" is not being maintained. Before the Spirit can fill, a body must be prepared. The graft must have grown into the stem before the sap can begin to flow to produce fruit. In lowly obedience we are to follow Christ, even in external matters, denying ourselves, forsaking the world, and even in the body seeking to conform to Him as we abide in Him so that we will be able to receive and enjoy the "I in you." His "Abide in Me" will prepare us for the work undertaken by Him: "I in you."
And, how do we "Abide in Him?" Once again, a very simple answer, which mankind fails to grasp: LOVE. To love God with all of our heart, mind and soul. And, to love unconditionally all others.