Charles Spurgeon Commentary Romans 12:2

"And be not fashioned according to this world: but be ye transformed by the renewing of your mind, and ye may prove what is the good and acceptable and perfect will of God." — Romans 12:2 (ASV)

And be not conformed to this world:

Do not live as people of the world do. Do not follow the customs, the fashions, the principles of the world. Be not conformed to this world.

But be ye transformed

It is not enough to be nonconformists. Be transformed ones, altogether changed into another form.

By the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.

It is by holy living, by consecrated bodies, that we are to prove the will of God. We cannot know it, we cannot practically work it out, except by a complete consecration to God.