I would offer.. (sorry for the length).
God has designed mankind to to serve the Creator. Mankind fell when they performed the will of another. The god of this world . The letter of the law "death" You shall surely die) began the glory of God departed. But the letter continues to do its work of showing we are guilty before God.
God has set eternity in the hearts of man yet mankind's hard heart cannot understand .
Ecclesiastes 3:11 New King James Version (NKJV) He has made everything beautiful in its time. Also He has put eternity in their hearts, except that no one can find out the work that God does from beginning to end.
Christians as new creatures walk by faith (hearing the word of God the gospel) and not by sight. Its a evil generation that seeks after a sign, the temporal seen before they will beleive. the unbelieving Jew performed that with Jesus making him into a circus seal . Show us a miracle then we will believe. (John 6:30)
When Cain heard the gospel it conflicted with his conscience offending him, he became angry and he murdered Abel the first martyr. The foundation of Paganism. Out of sight out of mind.
The mark is the mark of Cain the unseen law that works in the heart of mankind spoken of in Roman 2 accusing and excusing.
Roman 2: 11-15
For there is no respect of persons with God. For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law; (For not the hearers of the law are just before God, but the doers of the law shall be justified. For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another
In Romans 2:16 we are informed that women exchanged their natural function for that which is against nature. They know it is against nature, “They knew God.” focusing the point that every human being is guilty before God because every one of us, “suppress the truth” In our actions. Only Jesus performed it perfectly.
None of us lives up to the demands of his own conscience as a judgement hall . One minute accusing ourselves the next excusing) let alone the demands that God has given .Only in Christ our sabbath rest. . can we know what God has written in our hearts .
Then having the power sealed or marked in the forehead (mind) as forgiven ones. We then can seek for strength to do the will
Revelation 7:3 Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads.
Having a new heart and power a mark of a new spirit
Hebrews 10: 15
Whereof the Holy Ghost also is a witness to us: for after that he had said before, This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them; And their sins and iniquities will I remember no more.
When Cain heard the unwritten law "thou shall not murder" having no faith by which he could believe God . In his mind he knew he deserves death offended by the gospel. he plowed Abel under (out of sight out of mind) The reckoning of a heart void the work of the gospel. out of sight out of mind.
Genesis 4: 13-15
And Cain said unto the Lord, My punishment is greater than I can bear. Behold, thou hast driven me out this day from the face of the earth; and from thy face shall I be hid; and I shall be a fugitive and a vagabond in the earth; and it shall come to pass, that every one that findeth me shall slay me. And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him.
His whole life he remained a restless wander always looking back. . no vision of rest ahead . No light on his path