2:3 endure hardness. “Endure hardness” is one word in the Greek (kakapatheo), the same word as in “suffer trouble” and “endure afflictions” (II Timothy 2:9; 4:5). A fruitful Christian life is inevitably accompanied by much opposition from the world, the flesh, and the devil, and Paul wanted to encourage young Timothy to stand strong, as he himself had done for so long.
2:3 soldier. The Christian is often compared in Scripture to a soldier, engaged in spiritual warfare with the hosts of darkness (II Corinthians 10:3-5; Ephesians 6:10-18; I Thessalonians 5:8).