The apostles claimed authority from God as they wrote by way of Holy Spirit inspiration:

I Corinthians 2:10-13... "For to us (apostles) God revealed them through the Spirit; for the spirit searches all things, even the depths of God. For who among men knows the thoughts of a man except the spirit of the man which is in him? Even so the thoughts of God no one knows except the Spirit of God. Now we have received, not the spirit of the world, but the Spirit who is from God, so that we may know the things freely given to us by God, which things we also speak, not in words taught by human wisdom, but in those taught by the Spirit, combining spiritual thoughts with spiritual words."

*Note that in this passage, the apostle Paul claims direct inspiration from God through the Spirit who gave him not only "spiritual thoughts" but also "spiritual words" to express those thoughts.

I Corinthians 14:37... The apostle Paul states, "If anyone thinks he is a prophet or spiritual, let him recognize that the things which I write to you are the Lord's commandment."

I Thessalonians 2:13... Here the apostle Paul says to the church at Thessalonica, "For this reason we also constantly thank God that when you received the word of God which you heard from us, you accepted it not as the word of men, but for what it really is, the word of God, which also performs its work in you who believe."

Ephesians 3:3-5... "...by revelation there was made known to me the mystery... the mystery of Christ, which in other generations was not made known to the sons of men, as it has now been revealed to His holy apostles and prophets in the Spirit."

Colossians 4:16... The apostle Paul intended that his epistles (New Testament letters, books) be read in the church and shared among the various churches: "When this letter is read among you, have it also read in the church of the Laodiceans; and you, for your part read my letter that is coming from Laodicea."

I Thessalonians 5:27... "I adjure you by the Lord to have this letter read to all the brethren!"

2 Thessalonians 2:15... "So then, brethren, stand firm and hold to the traditions which you were taught, whether by word of mouth or by letter from us."

2 Timothy 1:13... Here the apostle Paul asserts his "apostolic authority" in the fact that His teachings contain the "pattern of sound words" and that Timothy and the church must hold to that pattern: "Hold to the pattern of sound words which you have heard from me, in the faith and love which are in Christ Jesus."

2 Peter 1:15-16... The apostle Peter asserts his "apostolic authority" to write to them as one who was an "eyewitness" of Christ: "And I will also be diligent that at any time after my departure [death] you will be able to call these things to mind. For we did not follow cleverly devised tales when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of His majesty."

2 Peter 3:1-2... "This is now, beloved, the second letter I am writing to you in which I am stirring up your sincere mind by way of reminder, that you should remember the words spoken beforehand [Old Testament] by the holy prophets and the commandment of the Lord and Savior [New Testament] spoken by your apostles."