Here the reference appears to be to Gaius’ spiritual life, which was strong. It is possible that his physical condition was not so good. He may have neglected the physical concerns of life for the religious. Such neglect is harmful; balance is essential to successful living. The enemy of souls is also well aware of the importance of balance, and seeks to drive earnest Christians into extreme positions (MH 318-324). The combination of a balanced health program with genuine spiritual advancement will prepare us to overcome the temptations of modern life and help us to meet the high standard set for entrance to heaven (2T 375, 376).

All who are followers of Christ may well make John’s prayer for Gaius their own, for themselves, their households, and their fellow believers.

 Gr. hugiainō (cf. our word “hygiene”), “to be sound,” “to be in good health,” and so used by the physician Luke (Luke 5:31; 7:10; 15:27). Paul uses it of those who are “sound in faith” (Titus 1:13; 2:2). God is interested in our physical condition, and wants us to enjoy the best of health. Because of the close connection between mind and body, when the soul or character prospers, the body is better able to be healthy (Ex. 15:26; Prov. 14:30; MH 241). Conversely, when the health of the body is neglected and bad physical habits are established, the religious life also suffers (MH 280, 315, 319).

 The clause literally reads “concerning all things, I wish [or, “pray”] thee to prosper.” This rendering reveals a more balanced desire on John’s part: he is not supremely concerned about prosperity and health, as the KJV implies, but has general prosperity in mind, thus covering spiritual as well as material well-being. John’s prayer illustrates a good habit for Christians to form; remembrance of a friend should stimulate prayer on his behalf (cf. on Phil. 1:3, 4; 1 Thess. 1:2, 3).

 See on v. 1.

 Gr. euodoō, originally, “to have a prosperous journey,” then used in a general sense, “to be successful,” “to prosper” (cf. 1 Cor. 16:2). The Lord is not unmindful of our temporal needs. He wants us to succeed in our temporal as well as our spiritual affairs. A good Christian should be a good businessman, or workman, since, in addition to natural ability he may also enjoy the blessing of God on his daily duties.