A.T. Robertson 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)

Be not fashioned (μη συνσχηματιζεσθε). Present passive imperative with μη, stop being fashioned or do not have the habit of being fashioned. Late Greek verb συσχηματιζω, to conform to another's pattern (1 Corinthians 7:31; Php 2:7f.). In N.T. only here and 1 Peter 1:14.

According to this world (τω αιων τουτω). Associative instrumental case. Do not take this age as your fashion plate.

Be ye transformed (μεταμορφουσθε). Present passive imperative of μεταμορφοω, another late verb, to transfigure as in Mt 17:2 ; 2 Corinthians 3:18, which see. On the distinction between σχημα and μορφη, see Php 2:7. There must be a radical change in the inner man for one to live rightly in this evil age, "by the renewing of your mind" (τη ανακαινωσε του νοος). Instrumental case. The new birth, the new mind, the new (καινος) man.

That ye may prove (εις το δοκιμαζειν). Infinitive of purpose with εις το, "to test" what is God's will, "the good and acceptable and perfect" (το αγαθον κα ευαρεστον κα τελειον).