How many good duties are lost and spoiled by sinful indulgence to our bodies? Alas! we are generally more solicitous to live long, than to live usefully. How many saints have active, vigorous bodies, yet God hath little service from them. If your bodies were animated by some other souls that love God more than you do, and burn with holy zeal to his service, more work would be done for God by your bodies in a day, than is now done in a month. To have an able, healthy body, and not use it for God, for fear of hurting it, is as if one should give you a strong and stately horse, upon condition you must not work or ride him. Wherein is the mercy of having a body, exeept it be employed for God? Will not its reward at the resurrection be sufficient for all the pains you now put it to in his service?
The Whole Works of the Reverend John Flavel, 1:497–498.