2 Tim 1:1

Paul, an apostle of Christ Jesus by the will of God according to the promise of the life that is in Christ Jesus
2 Tim 1:1

Paul introduces himself as an apostle of the Lord Jesus Christ.

NBD on Apostle: The sense of ‘sent one, messenger’ may have survived in popular speech: at least, isolated occurrences in the LXX and Josephus suggest that this meaning was recognized in Jewish circles. Only with Christian literature, however, does it come into its own. In NT it is applied to Jesus as the Sent One of God (Heb. 3:1), to those sent by God to preach to Israel (Lk. 11:49) and to those sent by churches (2 Cor. 8:23; Phil. 2:25); but above all it is applied absolutely to the group of men who held the supreme dignity in the primitive church. Since apostelloœ seems frequently to mean ‘to send with a particular purpose’, as distinct from the neutral pempoœ (save in the Johannine writings, where the two are synonyms), the force of apostolos is probably ‘one commissioned’—it is implied, by Christ.

By the will of God:The greek word here is Thelema which means "of what God wishes to be done by us; commands, precepts"

Quoted pg 48 : Knowing God's WIll by Smith
... whenever NT refers to our responsibility for knowing or doing God's will, the Greek term used for will is always thelema, which generally implies not God's resolute intention but simply his wish or desire, which requires our cooperation for its fulfillment. When Paul states, for instance, "this is the will of God, your sanctification; that you abstain from unchastity" (1 Thess 4:3), he's not talking about something God plans to do regardless of our cooperation. Rather, he's stating a wish God has for our behaviour- one which we can choose to obey or not.

When friends desert us and opposition becomes intense there is nothing that gives Christians confidence like the assurance that we are doing God's will.

Matthew Henry:
The promise of eternal life to believers in Christ Jesus, is the leading subject of ministers who are employed according to the will of God.

According to the promise of the life: the apostle said his calling as an apostle was "according to" (i.e., "because of," or
"in harmony with," or both) "the promise of life in Christ Jesus" (v. 1). This promise is part of the gospel message"

. . . Paul in his circumstances probably thinks of 'life' (eternal) as something yet to be fully obtained—thus the reference to a promise (compare 1 Tim 6:19)." Philip H. Towner, 1-2 Timothy & Titus, p. 155.

Reflections:

1) Paul displayed obedience even unto death. Not forgetting that he is writing this in his death cell in Rome (most probably winter too), this is an encouragement to persevere to the end. How far will one go for the lord, to preach His word- even in the midst of rejection?

2) Paul had a role to play in God's plan for reaching the world for Jesus Christ, and his role was apostle - a unique ambassador from God to the world. Just as Paul had his role to play, we all have our role to play - what's yours?

3) Ryan: This verse can be broken down into 3 parts:
(i) "Paul, an apostle (special messenger) of Christ Jesus" - identity
(ii) "by the will of God"- active obedience (sidenote: see discussion on thelema, in which i disagree with NLT's 'chosen by the will of God'; surprisingly, the Message carried the right idea: "carrying out God's plan")
(iii) "according(because of) to the promise of the life that is in Christ Jesus" - the reason/purpose for such obedience/suffering

Paul actively choose to be God's special messenger, which is doing God's will, driven by the promise of the 'free' life in Christ. He experiences freedom despite the prison. He choose to be God's special messenger despite the suffering. He knows who he belongs to in face of rejection. The calling that God has given to us need to be actively obeyed. It will not be easy. It may take us to places dangerous or unchartered waters. But God's promise of eternal life hold fast. Do we set our sights further than the present? or are we living for the temporal? In face of difficulties, we must set our sight further - we can have hope because of the PROMISE of the life that is in Jesus Christ. It gives us hope to carry on, to persevere in light of the future glory in Christ. Be thou my vision.