en_tn_condensed/2th/02/15.md

So then, brothers, stand firm

Paul exhorts the believers to hold fast to their faith in Jesus.

hold tightly to the traditions

"remember the traditions" or "believe the truths"

you were taught

"we have taught you"

whether by word or by our letter

"whether by what we taught you in person or by what we wrote to you in a letter"