I. The sacred penman writes and sends the letter, referred to as "The elder," meaning by years and office, deserving honor. Some question whether this was John the apostle, but his style and spirit are evident. Gaius could not question who wrote it. John humbly refers to himself as "the elder," aligning with ordinary church pastors. II. The recipient is Gaius, a well-beloved individual, possibly the same Gaius mentioned by Paul in Romans 16:23. John expresses his love for him "in the truth," for walking in truth, which shows true love rooted in the gospel. III. John prays for Gaius, asking for the prosperity of both his soul and body. Soul prosperity is the greatest blessing, often housed in a fragile body, but the desire for both spiritual and physical well-being is evident.

I wish above all things - Περι παντων ευχομαι· Above all things I pray that thou mayest prosper, and be in health, και ὑγιαινειν· to which one MS. adds εν αληθεια, which gives it a different meaning, viz., that thou mayest be sound in the truth. The prayer of St. John for Caius includes three particulars:
1. Health of body;
2. Health of soul; and
3. Prosperity in secular affairs. That thou mayest Prosper and be in Health, as thy Soul Prospereth. These three things, so necessary to the comfort of life, every Christian may in a certain measure expect, and for them every Christian is authorized to pray; and we should have more of all three if we devoutly prayed for them.
It appears from the last clause that the soul of Caius was in a very prosperous state.

Beloved, I wish above all things that thou mayest prosper,.... Or succeed in all temporal affairs, in the business of life, in which he was; and as success of this sort depends upon the blessing of God, which maketh rich, it is to be wished and prayed for from him:

and be in health; that is, of body, which above all things above all outward mercies, is the most desirable; for without this, what are the richest dainties, the largest possessions, or the best of friends? without this there can be no comfortable enjoyment of either of them; and therefore of this sort of mercies, it is in the first place, and above all others, to be wished for, and desired by one friend for another. The rule and measure of this wish is according to the prosperity of his soul,

even as thy soul prospereth: the soul is diseased with sin, and may be said to be in good health, when all its iniquities are forgiven; and may be said to prosper, when having a spiritual appetite for the Gospel, the sincere milk of the word, it feeds upon it, is nourished by it, and grows thereby; when it is in the lively exercise of faith, hope, and love; when spiritual knowledge is increased, or it grows in grace, and in the knowledge of Christ Jesus; when the inward man is renewed day by day with fresh strength; and when it enjoys communion with God, has the light of his countenance, and the joys of his salvation; and when it is fruitful in every good work.

above all things--Greek, "concerning all things": so ALFORD: in all respects. But WAHL justifies English Version (compare Pe1 4:8). Of course, since his soul's prosperity is presupposed, "above all things" does not imply that John wishes Gaius' bodily health above that of his soul, but as the first object to be desired next after spiritual health. I know you are prospering in the concerns of your soul. I wish you similar prosperity in your body. Perhaps John had heard from the brethren (Jo3 1:3) that Gaius was in bad health, and was tried in other ways (Jo3 1:10), to which the wish, Jo3 1:2, refers.

prosper--in general.

be in health--in particular.