1 Timothy 1:8

But we know that the law is good
The apostle says this to prevent an objection that might be made to him, that seeing he bore so hard on such who were fond of being teachers of the law, he was himself against the law, and the preaching and proper use of it; but this he would not have concluded, for he and his fellow labourers in the ministry, and all true believers know, from the Scriptures of truth, from the agreement of the law with the Gospel, and from their own experience, that the law is good, provided it be used in a lawful way, and to lawful purposes: and this is to be understood not of the ceremonial law, which was now disannulled, because of the weakness and unprofitableness of it, so that there was no lawful use of that; but of the moral law, which must needs be good, since the author of it is God, who is only good; and nothing but good can come from him: the law, strictly moral, is a copy of his nature, transcribed out of himself, as well as with his own hands; and is a declaration of his will, and is stamped with his authority, and therefore must be good: the matter of it is good, it contains good, yea, great and excellent things; the matter of it is honestly and morally good, as to love mercy, do justice, and walk humbly with God: and it is pleasantly good to a regenerate man, who loves it, and delights in it after the inner man, and serves it with his spirit; though the carnal mind cannot be subject to it, but rejects it, and rebels against it: and it is also profitably good; for though obedience to it is not profitable to God, yet it is to men; and though eternal life is not obtained hereby, nor any reward given for keeping it, yet in keeping it there is a reward; and that peace is enjoyed, which the transgressors of it are strangers to: it is good in the uses of it, both to sinners and to saints. To sinners it is useful for the knowledge of sin, to convince of it, and bring them to a sense of it, and concern for it, which is effectually done, when the Spirit of God sets in with it, or brings this commandment home to the heart; and if it has not this use, it is sometimes a means of restraining men from sin, which is the use of civil laws among men; and if it has not this, it is of use however to accuse men rightly of sin, and to pronounce justly guilty before God for it, to curse them as they deserve it, and to sentence to condemnation and death: and to believers it is of use, though they are not under it as in the hands of Moses, and as a covenant of works, and are freed from its curse and condemnation, and under no obligation to seek for life and righteousness by it; to them it is of use, to point out to them what is the will of God, and what should be done, and not done; and it is a rule of walk and conversation to them, as in the hands of Christ; and is as a glass to them to behold their own deformity, the impurity of their nature, the plague of their own hearts, and the imperfection of their obedience; by which they see the insufficiency of their own righteousness, how far they are from perfection, and what carnal creatures they are, when compared with this law: and as this serves to put them out of conceit with themselves, so it tends to make Christ and his righteousness more lovely and valuable in their esteem; who has wrought out a righteousness as broad and as long as the law is, and by which it is magnified and made honourable, and has delivered them from its curse and condemnation. And this law is good as it is holy, in its author, nature, and use; and as it is just, requiring just things, and doing that which is just, by acquitting those who are interested in Christ's righteousness, and in condemning those that have no righteousness; and as it is a spiritual and perfect law, which reaches the spirit and soul of man, and is concerned with inward thoughts and motions, as well as outward actions; and especially the end of it, the fulfilling end of it is good, which is Jesus Christ, who was made under it, came to fulfil it, and has answered all the demands of it: so that it must be good, and which cannot be denied,

if a man use it lawfully;
for if it is used in order to obtain life, righteousness, and salvation by the works of it, or by obedience to it, it is used unlawfully: for the law does not give life, nor can righteousness come by it; nor are, or can men be saved by the works of it; to use the law for such purposes, is to abuse it, as the false teachers did, and make that which is good in itself, and in its proper use, to do what is evil; namely, to obscure and frustrate the grace of God, and make null and void the sufferings and death of Christ. A lawful use of the law is to obey it, as in the hands of Christ, the King of saints, and lawgiver in his church, from a principle of love to him, in the exercise of faith on him, without any mercenary selfish views, without trusting to, or depending on, what is done in obedience to it, but with a view to the glory of God, to testify our subjection to Christ, and our gratitude to him for favours received from him.