New Revised Standard Version
So then, brothers and sisters, stand firm and hold fast to the traditions that you were taught by us, either by word of mouth or by our letter.

Contemporary English Version
My friends, this is why you must remain faithful and follow closely what we taught you in person and by our letters.

New American Bible
Therefore, brothers, stand firm and hold fast to the traditions that you were taught, either by an oral statement or by a letter of ours.

Douay-Rheims Bible
Therefore, brethren, stand fast: and hold the traditions, which you have learned, whether by word or by our epistle.

Therefore, brethren, stand fast: and hold the traditions, which you have learned, whether by word or by our epistle.

stand.

1 Corinthians 15:58 Therefore, my beloved brethren, be ye steadfast and unmoveable: always abounding in the work of the Lord, knowing that your labour is not in vain in the Lord.

1 Corinthians 16:13 Watch ye: stand fast in the faith: do manfully and be strengthened.

Philippians 4:1 Therefore my dearly beloved brethren and most desired, my joy and my crown: so stand fast in the Lord, my dearly beloved.

hold.

2 Thessalonians 3:6 And we charge you, brethren, in the name of our Lord Jesus Christ, that you withdraw yourselves from every brother walking disorderly and not according to the tradition which they have received of us.

1 Corinthians 11:2 Now I praise you, brethren, that in all things you are mindful of me and keep my ordinances as I have delivered them to you.

the traditions.

Romans 16:17 Now I beseech you, brethren, to mark them who make dissensions and offences contrary to the doctrine which you have learned and avoid them.

Jude 1:3 Dearly beloved, taking all care to write unto you concerning your common salvation, I was under a necessity to write unto you: to beseech you to contend earnestly for the faith once delivered to the saints.

*Gr:

whether.

2 Thessalonians 2:2 That you be not easily moved from your sense nor be terrified, neither by spirit nor by word nor by epistle. as sent from us, as if the day of the Lord were at hand.

2 Thessalonians 3:14 And if any man obey not our word by this epistle, note that man and do not keep company with him, that he may be ashamed.