3:3 ἀπεθάνετε γάρ, καὶ ἡ ζωὴ ὑμῶν κέκρυπται σὺν τῷ Χριστῷἐν τῷ θεῷThe aorist is simply a powerful metaphor for the fact that when they believed in Christ in baptism they were putting their previous way of life to death and having it buried out of sight. Consequently, it should no longer be a factor in their new way of life, determined not by their old fears and loyalties but by their new and primary loyalty to Christ and by the enabling which comes from on high (1:11,29).....The rhetorical character of the bare aorist formulation here, as also at the beginning of chapter 6&7&8 of Romans, needs to be recognized. Its object is to ensure that the change of perspective marked by conversion-initiation is final and fixed.The other side of this death with Christ, already stated in 3:1, is now restated in a variant formulation: "your life has been hidden with Christ in God." The thought once again is probably apocalyptic in character.
-p.207The undisputed Paulines do not use the verb κρυπτω (though they do use the related adjective); but the theme of hiddenness has been a feature earlier in the letter, where the compounds αποκρυπτω and αποκρυφος were used (1:26, 2:3). The "hiddenness" in mind here is the therefore probably the hiddenness of the divine mystery (1:26) and of "all the treasures of wisdom and knowledge" (2:3)... it refers to a hidden reality... that is actually determining the outworkings of history and is the true source of wisdom and knowledge (cf. 1Cor.2:6-16)
-"In God" is an unusual Pauline formulation (only in 1Ts.1:1; 2Ts.1:1, cf.Eph.3:9), but its christological weight is wholly of a piece with the Wisdom christology of the hymn in 1:15-20.Paul and Timothy were evidently wholly confident that this perspective, this hidden resource, would provide all the wisdom needed to cope with the challenges and problems of daily living.