Romans 5:13,14

Rom. 5:13, 14. "For until the Law sin was in the world: but sin is not imputed when there is no law. Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of Him that was to come." There are two things the Apostle would prove in these words, one of which establishes the other. First, he would prove that all mankind were under the law God gave to Adam, that stated "death to be the wages of sin." This is evident, because that sin, as bringing death, was in the world before there was any other legislation or scheme, giving of law to mankind, besides what was to Adam, viz., in that space of time that was from Adam to Moses. There being sin, therefore, in the world, as bringing death in that space of time, before the giving of the Law by Moses, shows that there was a Law given of God before that time, threatening death that they were under; but this could be no other than the Law God gave to Adam. This proves that Adam was the legal head of mankind; that mankind were under the Law given to him, wherein God threatened death for transgression; and thus God, in this Law given to Adam, saying, "When thou sinnest thou shalt die," did not only speak to him, though He spoke in the singular number; but in him spoke to posterity also. Hereby the Apostle prepares the way for the second thing he would prove in these words which he had asserted before, Romans 5:12, "Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned;" which he mainly aims at the proof, viz., that all mankind sinned and fell in Adam. This is evident by Adam's being the legal head of mankind, which is the first thing insinuated. For if God, when He spoke to Adam in the singular number, giving him a precept, spoke to him as representing posterity, so it will follow that He spoke to him as representing his posterity in the threatening; and this is further evident by this, that death did not only reign from Adam to Moses, but also reigned over them that had not violated Adam's law themselves by their actual personal transgression, as Adam had done.

Rom. 5:18