15 Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.
Paul says here to stand fast. There are other places of note where to stand fast is said to be important. Paul tells the Corinthians to stand fast in the faith, letting all of their efforts be done with brotherly love.
1Corinthians 16:13 Watch ye, stand fast in the faith, quit you like men, be strong. 14 Let all your things be done with charity.
In not getting entangled again with the Law given to Moses lest any man should fool himself by thinking that he was saved from eternal damnation by following that Law in any respect, and not Christ alone.
Galatians 5:1 Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage. 2 Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing. 3 For I testify again to every man that is circumcised, that he is a debtor to do the whole law. 4 Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace. 5 For we through the Spirit wait for the hope of righteousness by faith. 6 For in Jesus Christ neither circumcision availeth any thing, nor uncircumcision; but faith which worketh by love.
In the Philippians’ suffering.
Philippians 1:27 Only let your conversation be as it becometh the gospel of Christ: that whether I come and see you, or else be absent, I may hear of your affairs, that ye stand fast in one spirit, with one mind striving together for the faith of the gospel; 28 And in nothing terrified by your adversaries: which is to them an evident token of perdition, but to you of salvation, and that of God. 29 For unto you it is given in the behalf of Christ, not only to believe on him, but also to suffer for his sake; 30 Having the same conflict which ye saw in me, and now hear to be in me.
Philippians 4:1 Therefore, my brethren dearly beloved and longed for, my joy and crown, so stand fast in the Lord, my dearly beloved.
1Thessalonians 3:8 For now we live, if ye stand fast in the Lord.
Traditions are commandments or doctrines which tell us how we are to live.
Matthew 15:3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?...6 And honour not his father or his mother, he shall be free. Thus have ye made the commandment of God of none effect by your tradition.
Mark 7:9 And he said unto them, Full well ye reject the commandment of God, that ye may keep your own tradition.
The doctrines that Paul taught were taught by him directly to the Thessalonians and also by the letters he sent. An epistle is a letter.
2Corinthians 3:1 Do we begin again to commend ourselves? or need we, as some others, epistles of commendation to you, or letters of commendation from you?
2Corinthians 7:8 For though I made you sorry with a letter, I do not repent, though I did repent: for I perceive that the same epistle hath made you sorry, though it were but for a season.
There are a lot of reasons to stand fast in the faith in these letters to the Thessalonians.
16 ¶ Now our Lord Jesus Christ himself, and God, even our Father, which hath loved us, and hath given us everlasting consolation and good hope through grace, 17 Comfort your hearts, and stablish you in every good word and work.
Consolation is the bringing of comfort in the face of difficulties and grief.
Jeremiah 16:7 Neither shall men tear themselves for them in mourning, to comfort them for the dead; neither shall men give them the cup of consolation to drink for their father or for their mother.
Philippians 2:1 If there be therefore any consolation in Christ, if any comfort of love, if any fellowship of the Spirit, if any bowels and mercies,
The fellowship of Christians together is supposed to bring this consolation and comfort as they encourage each other and worship God in unity.
Romans 15:5 ¶ Now the God of patience and consolation grant you to be likeminded one toward another according to Christ Jesus: 6 That ye may with one mind and one mouth glorify God, even the Father of our Lord Jesus Christ.
By His love God has given us consolation, comfort, and hope through His grace. Our speech and our good works manifest that we belong to the God who created all things. Or at least they are supposed to do that.
Christians are called to good works……
Ephesians 2:10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
…and good words.
Colossians 4:6 Let your speech be alway with grace, seasoned with salt, that ye may know how ye ought to answer every man.
By the way, hateful speech, paranoia, fear of the world, and self-righteous Phariseeism are not in any list of good works in the Bible.
With regard to good works, note the Bible’s definition of religion.
James 1:27 Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.