Don't Be A Fruitless Sap

This is quoted by Jonathan Edwards in Religious Affections:

“To profess to know much is easy; but to bring your affections into subjection, to wrestle with lusts, to cross your wills and yourselves, upon every occasion, this is hard. The Lord looketh, that in our lives we should be serviceable to him, and useful to men. That which is within, the Lord and our brethren are never better for it: but the outward obedience, flowing thence, glorifieth God and does good to men. The Lord will have this done. What else is the end of our planting and watering, but that the trees may be filled with sap? And what is the end of that sap, but that the trees may bring forth fruit? What careth the husbandman for leaves, and barren trees?” John Preston, The Church’s Carriage, The Golden Scepter with the Church’s Marriage and the Church’s Carriage in Three Treatises (London, 1638), pp.101-102