Matthew Poole and continuators on James 1:15

15 Then when lust hath conceived , it bringeth forth sin, and sin when it is finished , bringeth forth death .

Lust (compared to an Harlot) may be said to conceive, when the Heart is pleased with the motion, and yields some consent to it.

The Birth of Sin may be the complete consent of the Will to it, or the outward act of it.

Actual Sin the Fruit and Product of Original.

Sin is finished, when it is not only committed, but continued in, as the Way and Course of a Man's Life.

Not only temporal, but eternal: Or we may thus take the Order and Progress of Sin: The first indeliberate motion of Lust, is the Temptation or Bait, which by its Pleasantness enticeth, and by its Vehemency draws the Heart after it (as the Harlot, Pro. 7.21. with the flattering of her Lips forced the young Man, telling him of the Pleasure he should enjoy, v. 14, 16, 17, 18. and then he goes after her, v. 22.) the Hearts lingring about, and being entangled with the delightful motion of Lust, is its committing Folly with it, when the full consent is joined, Lust hath conceived; when the outward Act is performed, Sin is brought forth; and when Sin is finished in a setled Course, it brings forth Death; which, tho every Sin do in the merit of it, yet Sin only finished, doth in the Event. Object. Doth not this imply Lust, and its first motions not to be Sin? Answ. No: for, 1. the least motions of it are forbidden, Matth. 5.28. Rom. 7.7. 2ly. It is contrary to the Law and Spirit of God, Rom. 7.23, 25. Gal. 5.16, 17. 3ly. It is the Fountain of Impurity, and therefore is it self impure, Iob 14.4. Matth. 7.15, 16. Iames 3.11. 4ly. Evil Thoughts defile a Man, Matth. 15.19. Acts 8.22. Obj. How is Lust said here to bring forth Sin, when Rom. 7.8. Sin is said to work Lust? Ans. Iames calls the corrupt Principle it self, Lust, and the actings of it, Sins; whereas Paul calls the same Principle, Sin, and the actings of it, Lusts. And so both are true, Lust, as a Root, brings forth the acts of Sin as its Fruit s; and Sin, as a Root, brings forth actual Lusts, as its Fruits.