For instance, Cain was the first man guilty of murder when he struck Abel and killed him. This was not a transgression of any law as Abel's murder occurred somewhere around 1,500 years before Noah's flood, after which God issued a prohibition and punishment for murdering people in Genesis 9:6: "Whoever
sheds man's blood, By man his blood shall be shed;
For in the image of God He made man." There have always been negative consequences for sin (for the soul that sins will surely die), but God graciously spelled this out so people could recognise sin and avoid doing it. There was no prohibition for priests drinking wine while they were serving in tabernacle until Aaron's sons transgressed by offering "strange fire," burning incense when they should not have. It was then God gave the command the priests were not to drink when they entered the Tabernacle to serve so they could tell the difference between holy and unholy (Lev. 10:8-11).
I noticed this pattern throughout the Old Testament, that it was not until man sinned that God held forth laws and statutes to guide the people to avoid wickedness they naturally drank like water. In regard to specific sexual sins, God said in Leviticus 18:26-30: "You shall therefore keep My statutes and My judgments, and shall
not commit any of these abominations, either any of your own
nation or any stranger who dwells among you 27 (for all these abominations the men of the land have done, who
were before you, and thus the land is defiled), 28 lest the land vomit you out also when you defile
it, as it vomited out the nations that were before you. 29 For whoever commits any of these abominations,
the persons who commit them shall be cut off from among their people. 30 Therefore you shall keep My
ordinance, so that you do not commit any of these abominable
customs which were committed before you, and that you do not defile yourselves
by them: I am the LORD your
God." The reason why God forbade sinful sexual practices is because they were rife and leading people painfully to their destruction.
The fact God laid down prohibitions for sin after they were common practices is instructive for us today. There are times we do not realise we sinned until after the fact, but God would have His people respond in repentance to His word and the conviction of the Holy Spirit. We often learn more by failure than by our success, for by our failures we see our need for forgiveness and salvation. Rather than being governed by laws written on tablets of stone, born-again Christians are to be guided by love--God's love demonstrated to us by Jesus when He laid down His life on Calvary, washed the disciple's feet, extended mercy, compassion, was patient and graciously restored Peter who denied Him. Praise the LORD He holds us to higher standard than the letter of the law with the indwelling Holy Spirit so we might grow spiritually to maturity by His grace.