What were the Traditions Mention in 2 Thessalonians 2:15?

In 2 Thessalonians 2, the Apostle Paul is addressing the coming Man of Lawlessness to a church that believes the return of Christ could be at any moment. Now who exactly is this Man of Lawlessness is subject for another time but the point that is being addressed is Paul giving the church a warning that this was coming. Another thing that was coming would be people believing in falsehood due to this Man of Lawlessness.

At the end of chapter 2, Paul said:

But we should always give thanks to God for you, brothers beloved by the Lord, because God has chosen you as the first fruits for salvation through sanctification by the Spirit and faith in the truth. It was for this He called you through our gospel, that you may obtain the glory of our Lord Jesus Christ. So then, brothers, stand firm and hold to the traditions which you were taught, whether by word of mouth or by letter from us. Now may our Lord Jesus Christ Himself and God our Father, who has loved us and given us eternal comfort and good hope by grace, encourage your hearts and strengthen them in every good work and word (2 Thessalonians 2:13-17, LSB).

Paul tells the Thessalonian church that were loved by God, chosen by Him to obtain salvation, and to stand firm to the traditions they were taught. What are these traditions Paul is referring to? One of the authorities the Roman Catholic church believe they have is traditions passed down by the church fathers. That is not what Paul is saying in 2 Thessalonians 2:15.

The tradition Paul is, as Matthew Henry said, "the doctrine of the gospel, which had been delivered by the apostle, by word or epistle." It is sound doctrine that Paul is saying are the traditions under the Apostolic authority. The Thessalonian church was not the first to receive a command similar to this one:

Now I praise you because you remember me in everything and hold firmly to the traditions, just as I delivered them to you (1 Corinthians 11:2).

Hold to the standard of sound words which you have heard from me, in the faith and love which are in Christ Jesus (2 Timothy 2:13).

The same is true for us as we have God's inspired Word as we walk with Jesus in a world that has rejected him:

But thanks be to God that though you were slaves of sin, you obeyed from the heart that pattern of teaching to which you were given over (Romans 6:17). 

And we have as more sure the prophetic word, to which you do well to pay attention as to a lamp shining in a dark place, until the day dawns and the morning star arises in your hearts (2 Peter 1:19).

The Bible gives us the "traditions" we need. Man made traditions can be good depending on what they are but the traditions the Apostle Paul mentioned was one of sound doctrine not anything that was man made.