From The Existence and Attributes of God:
A carnal worship, whether under the law or gospel, is, when we are busied about external rites, without an inward compliance of soul. God demands the heart; ‘My son, give me thy heart;’ not give me thy tongue, or thy lips, or thy hands; these may be given without the heart, but the heart can never be bestowed without these as its attendants. A heap of services can be no more welcome to God, without our spirits, than all Jacob’s sons could be to Joseph, without the Benjamin he desired to see. God is not taken with the cabinet, but the jewel; he first respected Abel’s faith and sincerity, and then his sacrifice; he disrespected Cain’s infidelity and hypocrisy, and then his offering. For this cause he rejected the offerings of the Jews, the prayers of the Pharisees, and the alms of Ananias and Sapphira, because their hearts and their duties were at a distance from one another. In all spiritual sacrifices, our spirits are God’s portion. Under the law, the reins were to be consumed by the fire on the altar, because the secret intentions of the heart were signified by them, (Psalm 7:9), ‘The Lord tries the heart and the reins’…Sincerity is the salt which seasons every sacrifice. The heart is most like to the object; and a spiritual soul is the spring of all spiritual actions. How can we imagine God can delight in mere service of the body, any more than we can delight in converse with a carcass? Without the heart it is no worship; it is a stage play; an acting a part without being that person really which is acted by us.
