3:21 Unto him [be] glory in the church by Jesus Christ. Let the church in all ages manifest his glory by its light.
Throughout all ages. Literally, Unto all the generations of the age of ages. The idea is, through the endless succession of ages, or through all time.
3:21 In the church - On earth and in heaven.
3:20,21 It is proper always to end prayers with praises. Let us expect more, and ask for more, encouraged by what Christ has already done for our souls, being assured that the conversion of sinners, and the comfort of believers, will be to his glory, for ever and ever.
