Having begun the passage with thanksgiving, Paul now closes it with a doxology. Eternal literally means “of the ages.” It refers to the two ages in Jewish thought, the present age, and the age to come. God had no beginning and will have no end. He exists outside of time, though He acts in it. He is immortal, imperishable, and incorruptible. He will never know death, decay, or loss of strength. Because God is invisible, He can be known only by His self-revelation. That He is the only God is a fundamental truth of Scripture (cf.. Deut. 4:35, 39; 6:4; Isa. 43:10; 44:6; 45:5–6, 21–22; 46:9; 1 Cor. 8:4, 6; 1 Tim. 2:5). He alone is worthy of all honor and glory forever and ever. The doxology closes with the emphatic Amen, meaning “let it be said.”
In contrast to the false gospel of the errorists, Paul emphasizes the true gospel and his participation in it by God’s grace. That grace is available to the worst sinner who comes to the Lord Jesus Christ in humble faith and repentance.
17 Paul concludes this section with a brief prayer or doxology, consisting of the following elements: (1) specification of the recipient (“to the King eternal [King of the ages] … the only God”); (2) ascription of praiseworthy attributes (“be honor and glory”); and (3) a solemn affirmation of the truth of the statement (“for ever and ever. Amen”; cf. Rev 1:6; 4:11; 5:12–13; 7:12). The doxology has a liturgical ring to it and may reflect Diaspora synagogue worship (cf. Tob 13:7, 11).
God’s eternal kingship is commonly acknowledged in the OT (esp. Jer 10:10; cf. Pss 10:16; 74:12). The term “immortal” is a Jewish import from Greek philosophy (Wis 12:1; Philo). “Invisible” casts God as incapable of being depicted in visual images (Ex 20:4–5; Col 1:15; Heb 11:27; cf. Jn 1:18; 5:37; 6:46; 1 Jn 4:20). Note that both characteristics, “immortal” and “invisible,” as well as “only,” resurface in the doxology at the end of the letter (6:15–16).
“Only God” (see Jude 25; cf. Jn 5:44) reflects the monotheism characteristic of both Judaism and Christianity (cf. Dt 6:4; Ro 3:29–30; 16:27; 1 Co 8:4–5; Gal 3:20; Eph 4:5–6). This contrasts sharply with the polytheism of the Greco-Roman world. With Paul, one may legitimately marvel that the transcendent, glorious God has in Christ Jesus come into the world to save sinners.
1:17 As Paul thinks of God’s marvelous dealings with him in grace, he bursts out into this lovely doxology. It is difficult to know whether it is addressed to God the Father or to the Lord Jesus. The words the King eternal seem to refer to the Lord Jesus because He is called the “Kings of kings, and Lord of lords” (Rev. 19:16). However, the word invisible seems to refer to the Father, since the Lord Jesus was obviously visible to mortal eyes. The fact that we are not able to distinguish which Person of the Godhead is intended might serve as an indication of Their absolute equality.
The King eternal is spoken of, first of all, as immortal. This means incorruptible or imperishable. God in His essence is also invisible. Men have seen appearances of God in the OT, and the Lord Jesus fully revealed God to us in visible form, but the fact remains that God Himself is invisible to human eyes. Next He is spoken of as God who alone is wise. In the final analysis, all wisdom comes from God (Jas. 1:5).
 MacArthur, J. F., Jr. (1995). 1 Timothy (pp. 32–33). Chicago: Moody Press.
 Köstenberger, A. (2006). 1 Timothy. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Ephesians–Philemon (Revised Edition) (Vol. 12, p. 507). Grand Rapids, MI: Zondervan.
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (pp. 2079–2080). Nashville: Thomas Nelson.