Adam Clarke on 1 Corinthians 7:5

Defraud ye not one the other - What ye owe thus to each other never refuse paying, unless by mutual consent; and let that be only for a certain time, when prudence dictates the temporary separation, or when some extraordinary spiritual occasion may render it mutually agreeable, in order that ye may fast and pray, and derive the greatest possible benefit from these duties by being enabled to wait on the Lord without distraction.

That Satan tempt you not for your incontinency - It is most evident that the separations permitted by the Apostle, for he enjoins none, are only for a season, on extraordinary occasions; and that the persons may come together again, lest Satan, taking advantage of their matrimonial abstinence, might tempt either party to illicit commerce.

There are a multitude of rules prescribed in such cases by the rabbins, and indeed even by heathen writers; for this was a matter in which common sense could always judge; and under the direction of experience, heathens, as well as those favored with Divine revelation, could see what was proper in all such cases.

Incontinence, εικρασια, want of strength to regulate one's desires or appetites; from α, negative, and κρατος, strength. It is remarkable that the apostle supposes that even this temporary continence might produce incontinence; and universal observation confirms the supposition.