en_tn/col/02/02.md

so that their hearts

Paul includes the Galatians even though he uses a different pronoun. AT: "so that their hearts and yours" (See: rc://en/ta/man/translate/figs-pronouns)

brought together

This means brought together in a close relationship.

all the riches of full assurance of understanding

Paul speaks of a person who is completely sure that the good news is true as though that person were rich in physical things. (See: rc://en/ta/man/translate/figs-metaphor)

the secret truth of God

This is knowledge that can be revealed only by God.

that is, Christ

Jesus Christ is the secret truth revealed by God.