en_tn_condensed/col/01/05.md

because of the hope reserved for you in heaven

Here "hope" stands for what the believer can confidently expect, that is, the things that God has promised to do for all believers. These things are spoken of as if they were physical objects that God was keeping in heaven for the believers to possess later. Alternate translation: "because of what you hope for that is reserved for you in heaven" or "because you are confident that God, who is in heaven, will do the many good things that he has promised you" (See: rc://en/ta/man/jit/figs-metonymy and rc://en/ta/man/jit/figs-metaphor)

the word of truth, the gospel

Possible meanings are 1) "the message about the truth, the gospel" or 2) "the true message, the gospel."