Walk In Him
"Walk in Him," we are told. What does that mean? "Walking" is about lifestyle. I think it means that our style of life is to reflect his. It means we are to be at home in him and that, being so at home, we are to behave as if conforming our ways to his were the most natural thing in the world.
We are to be "rooted in him:' Roots are living things. So to be rooted in him is to draw our principle of life from him. It is to wither from lack of conscious contact with him.
On the other hand, to be "built upon" him suggests that growth in him is not something that happens automatically. A house does not build itself but only happens as a result of human choice and execution. Holiness is not an accident but happens because human beings decide that their free choices, organically related, are governed by the pattern of his own self-giving.
Finally, to be "established" in him suggests that because of him our lives have a kind of official and divine significance, that they have this permanently, and that they have this in plain view, open to the entire world to see.
Father John Dominic Corbett, O.P.