Before faith came. That is, before the mystery of how God could save men by faith alone was clearly revealed in the incarnation, perfect life, vicarious death, and glorious resurrection of our Lord (1 Tim. 3:16; see on John 1:17; Gal. 3:14, 19; cf. on Luke 16:16). Note the emphasis on time in Gal. 3:23, 25.
Kept. Literally, “guarded,” so as to prevent escape.
Under the law. That is, under the legal system (see on ch. 2:16). “Under the law” here means to be under its jurisdiction, not its condemnation (see on Rom. 6:14).
The faith. See above under “before faith came.”
Afterwards be revealed. The faith of OT times was rewarded at the first advent of Christ (see Rom. 16:25, 26; Heb. 1:1, 2). Previous to the incarnation, the promise of a coming Redeemer required faith that God would fulfill the promise. With the coming of Jesus, faith met reality.