1. God promised to the partakers of the New Covenant that: He would write His laws "in their minds and on their hearts." (Hebrews 8:10) He would write in their hearts that which He'd previously written in stone (the Ten Commandments). (2 Cor. 3:3) we can declare as Jesus did: "I delight to do Thy will, yea, Thy law is within My heart." (Psalms 40:8) 2. Just as the blood of a beast ratified the Old Covenant, the blood of Jesus ratified the New Covenant. (Matt. 26:28) 3. Whatsoever was to be part of the New Covenant had to be added before it was ratified b/c: "if (a covenant) be confirmed, no man can disannuleth or addeth thereto". (Galatians 3:15) "For a testament is of force after men are dead otherwise it is of no strength at all while the testator liveth." (Hebrews 9:16) Jesus died on Friday, which means that Sunday keeping, even if begun on Resurrection morning, would have begun 2 days too late to be part of the New Covenant - which means the seventh day Sabbath of the Ten Commandments which are supposed to found written in the hearts of New Covenant Christians is still God's only New Covenant day of rest and Sunday observance is founded upon tradition of the Roman Catholic Church alone, according to their very own admission. Jesus says, "If ye love Me, keep My commandments."