2 Timothy 1:1-2. This is the salutation from Paul's second letter to Timothy. Paul introduces himself as "an apostle of Christ Jesus by the will of God according to the promise of the life which is in Christ Jesus," and he wishes his beloved child Timothy "Grace, mercy, and peace from God the Father and Christ Jesus our Lord."

Paul says he is an apostle according to the promise of life which is in Christ Jesus. There is no promise of life outside of Christ Jesus, without Him, there's only death. So everything we do as followers of Christ is according to the promise of life He gives. We want that life, we want others to have that life, so we do all in accordance with His will (or try to, at least). As we do, we see that His grace, mercy, and peace are fruits of being His followers and doing His will.

Jesus wants his apostles to do all according to the promise of life that He has given us, and He empowers us with his grace to do so; He heals us with His mercy when we fail; and He grants us His peace when we succeed. It is so beautiful, so hopeful, and so sustaining!