Anxiety is sinful when it reflects a spirit of unbelief in the gracious promises of a heavenly Father. Christ commands us not to seek what we should eat or drink and not to have an anxious mind (Luke 12:29). Paul says, “Be anxious for nothing, but in everything by prayer and supplication, with thanksgiving, let your requests be made known to God” (Phil. 4:6, NKJV).
Anxiety involves a troubling or tormenting fear about “what might be,” a sense of being left hanging. Neither Christ nor Paul demands stoical impassivity. Christ could be troubled in spirit (John 12:27; 13:21)—He felt deeply, without ever sinning. Paul says to be anxious for nothing, but uses the same word to express that he has no one who will “sincerely care for your state” (Phil. 2:20, NKJV). He explains to the Corinthians that he has a daily burden of “deep concern for all the churches” (2 Cor. 11:28, NKJV).
While there is clearly such a thing as legitimate and godly concern, our anxiety is often interwoven with a lack of trust in God, His providences, and His promises. That was clearly not the case for the Lord Jesus, though His faith would be tested to a degree far beyond ours. It was clearly a challenge for the Apostle. In our examples above, anxiety (actual or potential) is countered by explicit declarations of confidence in God concerning what lies ahead, or testimonies or instances of prayerful dependence on God in the midst of those troubles. Paul tells the Philippians to be anxious for nothing because he is doing precisely what he told them to do: taking all his concerns to the Lord in believing prayer, just as Christ did perfectly.