A.T. Robertson Commentary Colossians 4:3

"withal praying for us also, that God may open unto us a door for the word, to speak the mystery of Christ, for which I am also in bonds;" — Colossians 4:3 (ASV)

Withal (αμα). At the same time.

That God may open (ινα ο θεος ανοιξη). Common use of ινα and the subjunctive (aorist), the sub-final use so common in the N.T. as in the Koine.

A door for the word (θυραν του λογου). Objective genitive, a door for preaching. It is comforting to other preachers to see the greatest of all preachers here asking prayer that he may be set free again to preach. He uses this figure elsewhere, once of a great and open door with many adversaries in Ephesus (1 Corinthians 16:9), once of an open door that he could not enter in Troas (2 Corinthians 2:12).

The mystery of Christ (το μυστηριον του Χριστου). The genitive of apposition, the mystery which is Christ (2:2), one that puts out of comparison the foolish "mysteries" of the Gnostics.

For which I am also in bonds (δι' ο κα δεδεμα). Perfect passive indicative of δεω. Paul is always conscious of this limitation, this chain. At bottom he is a prisoner because of his preaching to the Gentiles.