Observe the holiness and perfection of God's law, which forbids the first motions and risings of sin in the heart. The laws of men take hold of actions; but the law of God goes further—it forbids not only sinful actions—but sinful desires.
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Since the precept about not coveting is general, it ought to be extended to all depraved and inordinate concupiscence, original and habitual as well as actual—whether this is determinate and voluntary or still indeterminate and only titillating. This is true in order that the perfect purity and holiness of the lawgiver may be noted (which will suffer not even the smallest taint of depraved concupiscence in man, but demands righteousness and holiness of every kind).
This corruption of nature is here forbidden, for it is truly and properly sin, Rom. 6:12 and 7:17. It is the flesh that lusteth against the Spirit, Gal. 5:18; and if sin, it must be contrary to and forbidden by the law.
God therefore commands a strong and ardent affection, an affection not to be impeded by any portion, however minute, of concupiscence. He requires a mind so admirably arranged as not to be prompted in the slightest degree contrary to the law of love.
Such motions are not consistent with the holiness and purity which God demands from us and the required perfection of loving God with the whole heart and all the strength; therefore they cannot but be depraved and lawless (anomoi).