Outward exercise profits physically, or as Paul says strictly, “bodily exercise is useful for a little.” Piety is spiritual exercise and demands as much constant vigilance as holy self-restraint, as complete subjection to the revealed will of God, as training for the games calls for habitual abstinence from every relaxing habit and daily practice toward the end in view. How little there is of the exercise of piety, compared to bodily exercise!
Piety is profitable for all things, having promise of life that is now and of that to come. Christianity can allow no reserve, though all is of grace, and from its very nature must have the entire man, dead to sin and alive unto God, right through the present life into eternity. And this practical scope of godliness is pre-eminent in the pastoral epistles; not so much heavenly privilege or dispensational peculiarity, but rather a sound and devoted life according to godliness. This the apostle presses on Timothy, as Timothy was bound to press it on others.
Adapted from W. Kelly