en_tn_condensed/col/04/03.md

General Information:

Here the word "us" refers to Paul and Timothy but not the Colossians. (See: rc://en/ta/man/translate/figs-exclusive)

God would open a door

Opening a door for someone is a metaphor for giving that person the opportunity to do something. Alternate translation: "God would provide opportunities" (See: rc://en/ta/man/translate/figs-metaphor)

open a door for the word

"make an opportunity for us to preach his message"

the mystery of Christ

This refers to the gospel of Jesus Christ, which was not understood before Christ came.

Because of this, I am chained up

Here "chained" is a metaphor for being in prison, though he probably also was physically attached to a chain. Alternate translation: "It is for proclaiming the message of Jesus Christ that I am now in prison" (See: rc://en/ta/man/translate/figs-metaphor)