Whatsoever we do of our own power and strength, that which is not wrought in us by His grace, without doubt is a work of the law, and avails nothing toward justification; but is displeasing to God, because of the unbelief wherein it is done. He that trusts in works does nothing freely and with a willing mind; he would do no good work at all if he were not compelled by the fear of hell, or allured by the hope of present good. Whereby it is plainly seen that they strive only for gain, or are moved with fear, showing that they rather hate the law from their hearts, and had rather there were no law at all. An evil heart can do nothing that is good. This evil propensity of the heart, and unwillingness to do good, the law betrays when it teaches that God does not esteem the works of the hand, but those of the heart.
Thus sin is known by the law, as Paul teaches; for we learn thereby that our affections are not placed on that which is good. This ought to teach us not to trust in ourselves, but to long after the grace of God, whereby the evil of the heart may be taken away, and we become ready to do good works, and love the law voluntarily; not for fear of any punishment, but for the love of righteousness. By this means one is made of a servant, a son; of a slave an heir.
We shall now come to treat more particularly of the text. Verse 1. "The heir, as long as he is a child, differeth nothing from a servant, though he be lord of all." We see that the children unto whom their parents have left some substance are brought up no otherwise than if they were servants. They are fed and clothed with their goods, but they are not permitted to do with them, nor use them according to their own minds, but are ruled with fear and discipline of manners, so that even in their own inheritance they live no otherwise than as servants. After the same sort it is in spiritual things. God made with His people a covenant, when He promised that in the seed of Abraham, that is in Christ, all nations of the earth should be blest. That covenant was afterward confirmed by the death of Christ, and revealed and published abroad by the preaching gospel. For the gospel is an open and general preaching of this grace, that in Christ is laid up a blessing for all men that believe.
Before this covenant is truly opened and made manifest to men, the sons of God live after the manner of servants under the law; and are exercised with the works of the law, altho they cannot be justified by them; they are true heirs of heavenly things, of this blessing and grace of the covenant; although they do not as yet know or enjoy it. Those that are justified by grace cease from the works of the law, and come unto the inheritance of justification; they then freely work those things that are good, to the glory of God and benefit of their neighbors. For they have possest it by the covenant of the Father, confirmed by Christ, revealed, published, and as it were delivered into their hands by the gospel, through the grace and mercy of God.
This covenant Abraham, and all the fathers which were endued with true faith, had no otherwise than we have: although before Christ was glorified this grace was not openly preached and published: they lived in like faith, and therefore obtained the like good things. They had the same grace, blessing, and covenant that we have; for there is one Father and God over all. Thou seest that Paul here, as in almost all other places, treats much of faith; that we are not justified by works, but by faith alone. There is no good thing which is not contained in this covenant of God; it gives righteousness, salvation, and peace. By faith the whole inheritance of God is at once received. From thence good works come; not meritorious, whereby thou mayest seek salvation, but which with a mind already possessing righteousness thou must do with great pleasure to the profit of thy neighbors.
Verse 2. "But is under tutors and governors until the time appointed of the Father." Tutors and governors are they which bring up the heir, and so rule him and order his goods that he neither waste his inheritance by riotous living, nor his goods perish or be otherwise consumed. They permit him not to use his goods at his own will or pleasure, but suffer him to enjoy them as they shall be needful and profitable to him. They keep him at home, and instruct him whereby he may long and comfortably enjoy his inheritance: but as soon as he arrives to the years of discretion and judgment, it cannot but be grievous to him to live in subjection to the commands and will of another.
In the same manner stands the case of the children of God, which are brought up and instructed under the law, as under a master in the liberty of sons. The law profits them in this, that by the fear of it and the punishment which it threatens, they are driven from sin, at least from the outward work: by it they are brought to a knowledge of themselves, and that they do no good at all with a willing and ready mind as becomes sons; whereby they may easily see what is the root of this evil, and what is especially needful unto salvation; to wit, a new and living spirit to that which is good: which neither the law nor the works of the law is able to give; yea, the more they apply themselves to it, the more unwilling they find themselves to work those things which are good.