When a man can and does entirely say, Not my will, but Thine be done – when he so wills the will of God as to do it – then he is one with God, one as a true son with a true father.
God’s life within him is the causing and bearing of his life. It is therefore absolutely and only of its kind, one with it more and deeper than words or figures can say. It is the life which is itself, only more of itself, and, more than that, which causes itself. When a man wills that his being is conformed to that Being of his origin, which is the life in his life, when a man thus accepts his own causing Life, and sets himself to live the will of that causing Life, humbly eager after the privileges of his origin, he thus receives God’s life into himself. He becomes, in the act, a partaker of the divine nature, a true son of the Living God, and an heir of all He possesses. By the obedience of a son, he receives into himself the very life of the Father.
Obedience is the joining of the links of the eternal round. Obedience is but the other side of the Creative will: Will is God's will, obedience is man’s will. The two make one. The root Life, knowing well the thousand troubles it would bring upon Him, has created, and goes on creating, other lives, that though incapable of self-being they may, by willed obedience, share in the bliss of His essential self-ordained being.
If we do the will of God, eternal life is ours – no mere continuity of existence, for that in itself is worthless as hell, but a being that is one with the essential Life.
George MacDonald, Your Life in Christ: The Nature of God and His Work in Human Hearts, 80.