1 Timothy 4:8

profiteth little--Greek, "profiteth to (but) a small extent." Paul does not deny that fasting and abstinence from conjugal intercourse for a time, with a view to reaching the inward man through the outward, do profit somewhat, Act 13:3; Co1 7:5, Co1 7:7; Co1 9:26-27 (though in its degenerate form, asceticism, dwelling solely on what is outward, Ti1 4:3, is not only not profitable but injurious). Timothy seems to have had a leaning to such outward self-discipline (compare Ti1 5:23). Paul, therefore, while not disapproving of this in its due proportion and place, shows the vast superiority of godliness or piety, as being profitable not merely "to a small extent," but unto all things; for, having its seat within, it extends thence to the whole outward life of a man. Not unto one portion only of his being, but to every portion of it, bodily and spiritual, temporal and eternal [ALFORD]. "He who has piety (which is 'profitable unto all things') wants nothing needed to his well-being, even though he be without those helps which, 'to a small extent,' bodily exercise furnishes" [CALVIN]. "Piety," which is the end for which thou art to "exercise thyself" (Ti1 4:7), is the essential thing: the means are secondary. having promise, &c.--Translate as Greek, "Having promise of life, that which now is, and that which is to come." "Life" in its truest and best sense now and hereafter (Ti2 1:1).

— Jamieson-Fausset-Brown Commentary (public domain)