Commandment 4 episode 5

Some Christians DO observe the 7th Day as their Sabbath, but Most Christians don’t keep this one.  So who is right and who is wrong?

For this Commandment the question of right and wrong involves the problem of us judging one another, as we do about many other things. It was a contentious issue between the Pharisees and Jesus in the Gospels and between Christians in the early church in the epistles. And we still judge each other today.  
Romans 14:1-6. Receive one who is weak in the faith, but not to disputes over doubtful things...One person esteems one day above another; another esteems every day alike. Let each be fully convinced in his own mind. He who observes the day, observes it to the Lord; and he who does not observe the day, to the Lord he does not observe it. 

What is the Scriptural reason for most Christians to not observe the 7th day?

New Testament scripture reveals that this commandment refers not to a ritual observance of one day in each week, but to the every-day life of faith, which is the rest that we enter into as Christians, in the finished work of Christ. This rest is spoken of in the epistle of Paul to the Hebrews. 
Hebrews 4:9-11 There remains therefore a rest for the people of God. 10. For he who has entered His rest has himself also ceased from his works as God did from His. Let us therefore be diligent to enter that rest, lest anyone fall after the same example of unbelief and disobedience. 
ALSO
Colossians 2:16-17 Therefore let no one judge you in food or in drink or regarding a festival or a new moon or Sabbath days, 17. which are a shadow of things to come but the substance is of Christ. 

Did Israel fully obey the Sabbath Rest?
Yes and no. They obeyed the seventh day but they missed the essential aspect of FAITH and trust in God. They were told to rest for one year in seven and enjoy relating to each other as a family and a community together and to watch God supernaturally grow the crops for them. So they failed to observe that for 490 years since the time of King Saul. Divide 490 by seven and you get seventy. The bible says that they would go into captivity for 70 years in Babylon because they failed to give the land rest… 
2 Chronicles 36:20-21  And to those who escaped from the sword he carried away to Babylon, where they became servants to him and his sons until the reign of the kingdom of Persia, 21. to fulfil the word of The Lord by the mouth of Jeremiah, until the land had enjoyed her Sabbaths, ... to fulfil seventy years.  
ALSO (concerning Israel)
Hebrews 4:4 For the Scripture mentions the seventh day saying: “And God rested on the seventh day from all His works”; and in another place: “They shall not enter My rest.”