[1.] First, From the common argument which he useth at first to those whom he would draw off from a more careful conversation, which is this: Do such a thing, it is but for once, and but little; others do the like, and demur not, or the best do as great matters as this comes to. It is but a small thing, considering the strait, or the advantage that may accrue. This is his usual note to candidate iniquity, as experience of all doth testify.
[2.] Secondly, That this is so is also evident from a consideration of the several ways and courses of sinners. Some are tempted and overcome by one kind of sin, and not at all urged to others. Some go to hell in a way of covetousness; others are pretty unblameable in most of their carriages, but are overcome by a proud humour; others are given to drink, and yet will not steal nor deal falsely; others take a more cleanly way to hell, rely upon their own righteousness, or are engaged in error, and their life otherwise smooth and fair. The Jews in Christ’s time were only engaged against Christ, and for their traditions, but not molested with temptations to open idolatry as formerly. Those who are ignorant are not troubled with temptations to despair, or inward terrors. The reasons of his dealing thus are these:—
[1.] First, He sees that one sin heartily prosecuted is enough to signify homage to him, and to give him possession. As we take possession of land by a turf or a twig, so by one sin admitted with full purpose of mind, Satan is let into the heart. As a penny will be sufficient earnest for a bargain of a thousand pounds, so may one sin be a pledge or earnest for the whole soul in a league with hell.
[2.] Secondly, He knows that one sin persisted in may be enough to destroy the soul; as one wound may kill, one leak may sink a ship.
[3.] Thirdly, He knows that one sin breaks the covenant of God, and turns the heart from him, if men give up themselves to it.
[4.] Fourthly, One sin wilfully pursued makes a man guilty of the breach of the whole law. It destroys love and respect to God, undervalues his authority, contemns his threatenings and promises.
[5.] Fifthly, One sin is enough to make way for more. Where Satan would have more, yet at first he is pleased with it as a hopeful beginning. It makes room enough for the serpent’s head, and then he will afterwards easily wind in his whole body.
Applic. This may warn us not to be emboldened to any sin by the plea of diminution; not to venture because it may seem little, or be but for once. A true Christian should be a perfect universalist; he should be universally against all sin, and universally for all duty.