There is one scripture more that I cannot wholly pass over, which, to me, seems a plain prohibition of polygamy, in Levit. xviii. 18. _Thou shalt not take a wife to her sister, to vex her, to uncover her nakedness, besides the other in her life-time._ This respects either incest or polygamy; one of which must be meant by _taking a wife to her sister_. Now it cannot be a prohibition of incest; because it is said, _Thou shalt not_ do it _in her life-time_; which plainly intimates, that it might be done after her death. Whereas it is certainly contrary to the law of God and nature, for a person to take his wife’s sister after her decease, as well as in her life-time. Therefore the meaning is, Thou shalt not take another wife to her whom thou hast married; by which means they will become sisters. And here is another reason assigned hereof, _viz._ the envy, jealousy, and vexation that would attend such a practice, as the taking another wife would be a means of vexing, or making her uneasy. And therefore the sense is, as is observed in the marginal reading; _Thou shalt not take one wife to another_; or, Thou shalt not have more wives than one. This is a plain prohibition of this sin; but whether some holy men, in following ages, understood the meaning of this law, may be questioned; and therefore they were not sensible of the guilt they hereby contracted. Thus we have considered some of the sins forbidden in this Commandment. Every particular instance of the breach hereof, would exceed our intended brevity, on the subject we are treating of. Therefore, We shall proceed to consider the aggravations, more especially, of the sins of fornication and adultery; which may also with just reason, be applied to all other unnatural lusts; which have been before considered as a breach of this Commandment. And, [1.] They are opposite to sanctification, even as darkness is to light, hell to heaven; thus the apostle opposes fornication and uncleanness, to it, 1 Thes. iv. 3, 7. [2.] These sins are inconsistent with that relation, we pretend to stand in, to Christ, as members of his body; inasmuch as we join ourselves in a confederacy with his profligate enemies, 1 Cor. vi. 15, 16. And to this we may add, that they are a dishonour to, and a defilement of our own bodies, which ought to be the temples of the Holy Ghost, and therefore should be consecrated to him. [3.] They bring guilt and ruin on two persons at once, as well as a blot and stain on each of their families, and a wound to religion by those who make any profession of it, as it _gives occasion to the enemies of the Lord to blaspheme_, Prov. vi. 33. 2 Sam. xii. 14. [4.] They bring with them many other sins; as they tend to vitiate the affections, deprave the mind, defile the conscience, and provoke God to give persons up to spiritual judgments, which will end in their running into all excess of riot.