"I am the Vine, ye are the branches." John 15:5
The connection between the vine and the branch is a living one. No external, temporary union will suffice; no work of man can effect it: the branch, whether an original or an engrafted one, is such only by the Creator's own work, in virtue of which the life, the sap, the fatness, and the fruitfulness of the vine communicate themselves to the branch. And just so it is with the believer, too. His union with his Lord is no work of human wisdom or human will, but an act of God, by which the closest and most complete life-union is effected between the Son of God and the sinner.
Andrew Murray (C)