Here we have, I. An exhortation to abound in holiness, to abound more and more in that which is good, Th1 4:1, Th1 4:2. We may observe, 1. The manner in which the exhortation is given - very affectionately. The apostle entreats them as brethren; he calls them so, and loved them as such. Because his love to them was very great, he exhorts them very earnestly: We beseech and exhort you. The apostle was unwilling to take any denial, and therefore repeats his exhortation again and again. 2. The matter of his exhortation - that they would abound more and more in holy walking, or excel in those things that are good, in good works. Their faith was justly famed abroad, and they were already examples to other churches: yet the apostle would have them yet further to excel others, and to make further progress in holiness. Note, (1.) Those who most excel others fall short of perfection. The very best of us should forget those things which are behind, and reach forth unto those things which are before. (2.) It is not enough that we abide in the faith of the gospel, but we must abound in the work of faith. We must not only persevere to the end, but we should grow better, and walk more evenly and closely with God. 3. The arguments with which the apostle enforces his exhortation. (1.) They had been informed of their duty. They knew their Master's will, and could not plead ignorance as an excuse. Now as faith, so knowledge, is dead without practice. They had received of those who had converted them to Christianity, or been taught of them, how they ought to walk. Observe, The design of the gospel is to teach men not only what they should believe, but also how they ought to live; not so much to fill men's minds with notions as to regulate their temper and behaviour. The apostle taught them how to walk, not how to talk. To talk well without living well will never bring us to heaven: for the character of those who are in Christ Jesus is this: They walk not after the flesh, but after the Spirit. (2.) Another argument is that the apostle taught and exhorted them in the name, or by the authority, of the Lord Jesus Christ. He was Christ's minster and ambassador, declaring to them what was the will and command of the Lord Jesus. (3.) Another argument is this. Herein they would please God. Holy walking is most pleasing to the holy God, who is glorious in holiness. This ought to be the aim and ambition of every Christian, to please God and to be accepted of him. We should not be men-pleasers, nor flesh-pleasers, but should walk so as to please God. (4.) The rule according to which they ought to walk and act - the commandments they had given them by the Lord Jesus Christ, which were the commandments of the Lord Jesus Christ himself, because given by authority and direction from him and such as were agreeable to his will. The apostles of our Lord Jesus Christ were only commissioned by him to teach men to observe all things whatsoever he had commanded them, Mat 28:20. Though they had great authority from Christ, yet that was to teach men what Christ had commanded, not to give forth commandments of their own. They did not act as lords over God's heritage (Pe1 5:3), nor should any do so that pretend to be their successors. The apostle could appeal to the Thessalonians, who knew what commandments he gave them, that they were no other than what he had received from the Lord Jesus. II. A caution against uncleanness, this being a sin directly contrary to sanctification, or that holy walking to which he so earnestly exhorts them. This caution is expressed, and also enforced by many arguments, 1. It is expressed in these words: That you should abstain from fornication (Th1 4:3), by which we are to understand all uncleanness whatsoever, either in a married or unmarried state. Adultery is of course included, though fornication is particularly mentioned. And other sorts of uncleanness are also forbidden, of which it is a shame even to speak, though they are done by too many in secret. All that is contrary to chastity in heart, speech, and behaviour, is contrary to the command of God in the decalogue, and contrary to that holiness which the gospel requires. 2. There are several arguments to enforce this caution. As, (1.) This branch of sanctification in particular is the will of God, Th1 4:3. It is the will of God in general that we should be holy, because he that called us is holy, and because we are chosen unto salvation through the sanctification of the Spirit; and not only does God require holiness in the heart, but also purity in our bodies, and that we should cleanse ourselves from all filthiness both of flesh and spirit, Co2 7:1. Whenever the body is, as it ought to be, devoted to God, and dedicated and set apart for him, it should be kept clean and pure for his service; and, as chastity is one branch of our sanctification, so this is one thing which God commands in his law, and what his grace effects in all true believers. (2.) This will be greatly for our honour: so much is plainly implied, Th1 4:4. Whereas the contrary will be a great dishonour. And his reproach shall not be wiped away, Pro 6:33. The body is here called the vessel of the soul, which dwells therein (so Sa1 21:5), and it must be kept pure from defiling lusts. Every one should be careful in this matter, as he values his own honour and will not be contemptible on this account, that his inferior appetites and passions gain not the ascendant, tyrannizing over his reason and conscience, and enslaving the superior faculties of his soul. What can be more dishonourable than for a rational soul to be enslaved by bodily affections and brutal appetites? (3.) To indulge the lust of concupiscence is to live and act like heathens? Even as the Gentiles who know not God, Th1 4:5. The Gentiles, and especially the Grecians, were commonly guilty of some sins of uncleanness which were not so evidently forbidden by the light of nature. But they did not know God, nor his mind and will, so well as Christians know, and should know, this his will, namely our sanctification in this branch of it. It is not so much to be wondered at, therefore, if the Gentiles indulge their fleshly appetites and lusts; but Christians should not walk as unconverted Gentiles, in lasciviousness, lusts, excess of wine, revellings, banquetings, etc. (Pe1 4:3), because those who are in Christ have crucified the flesh with its affections and lusts. (4.) The sin of uncleanness, especially adultery, is a great piece of injustice that God will be the avenger of; so we may understand those words, That no man go beyond or defraud his brother (Th1 4:6), in any matter - en tō pragmati, in this matter of which the apostle is speaking in the preceding and following verses, namely, the sin of uncleanness. Some understand these words as a further warning and caution against injustice and oppression, all fraud and deceit in our dealings with men, which are certainly criminal, and contrary to the gospel. And Christians should not impose upon the ignorance and necessity of those they deal with, and so go beyond them, nor should they by equivocations or lying arts defraud them; and although this may be practised by some and lie long undiscovered, and so go unpunished among men, yet the righteous God will render a recompence. But the meaning may rather be to show the injustice and wrong that in many cases are done by the sin of uncleanness. Not only are fornication and other acts of uncleanness sins against his own body who commits them (Co1 6:18), not only are they very injurious to the sinner himself both in soul and body, but sometimes they are very injurious, and no less than defrauding, acts of injustice to others, particularly to those who are joined together in the marriage covenant and to their posterity. And, as this sin is of such a heinous nature, so it follows that God will be the avenger of it. Whoremongers and adulterers God will judge, Heb 13:4. This the apostle had forewarned and testified by his gospel, which, as it contained exceedingly great and precious promises, so also it revealed from heaven the wrath of God against all ungodliness and unrighteousness among men, Rom 1:18. (5.) The sin of uncleanness is contrary to the nature and design of our Christian calling: For God hath called us not unto uncleanness, but unto holiness, Th1 4:7. The law of God forbids all impurity, and the gospel requires the greatest purity; it calls us from uncleanness unto holiness. (6.) The contempt therefore of God's law and gospel is the contempt of God himself: He that despises despises God, not man only. Some might possibly make light of the precepts of purity and holiness, because they heard them from men like themselves; but the apostle lets them know that they were God's commands, and to violate them was no less than to despise God. He adds, God hath given Christians his Spirit, intimating that all sorts of uncleanness do in an especial manner grieve the Holy Spirit, and will provoke him to withdraw from us; and also the Holy Spirit is given unto us to arm us against these sins, and to help us to mortify these deeds of the body, that we may live, Rom 8:13.