Promise of the life in Christ Jesus

2 Tim. 1:1-2 (ESV)
Paul, an apostle of Christ Jesus by the will of God according to the promise of the life that is in Christ Jesus,
[2] To Timothy, my beloved child:
Grace, mercy, and peace from God the Father and Christ Jesus our Lord.

According to the promise of the life that is in Christ Jesus. Christianity is life, it is life in Christ Jesus, life promised to us by God. We don’t find this life in ourselves. It is not in the law. It is in Christ Jesus, whose life we have been baptized into. Romans 6:4 (ESV)
We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life.

Buried with him into death, we were raised in him to walk in newness of life. In ourselves there is nothing but sin and death, but in Christ we have life. Paul is an apostle according to this promise, the gospel. An apostle speaks and does what has been given to him to speak and to do. He is sent on behalf of another, in this case Jesus Christ. We cannot read Paul as if he is speaking his own thoughts. These are the words Christ has given him to speak, they are truth, and in them is life in Jesus Christ.