What is the Biblical Basis for Christians keeping the Sabbath?

The Sabbath is mentioned about one hundred and forty-five times in the whole Bible (KJV), in the Old Testament the Sabbath is mentioned about ninety times and in almost all the texts it is an instruction to Israel to keep the Sabbath holy. Exodus 31:12 NASB >12 Now the Lord spoke to Moses, saying, 13 “Now as for you, speak to the sons of Israel, saying, ‘You must keep My Sabbaths; for this is a sign between Me and you throughout your generations, so that you may know that I am the Lord who sanctifies you. Exodus 35:1-3 NASB >35 Then Moses assembled all the congregation of the sons of Israel, and said to them, “These are the things that the Lord has commanded you to [a]do: > >2 “For six days work may be done, but on the seventh day you shall have a holy day, a Sabbath of complete rest to the Lord; whoever does any work on it shall be put to death. 3 You shall not kindle a fire in any of your dwellings on the Sabbath day.” But in the New Testament, it is mentioned about fifty-five times and in almost every text it is used as an index or marker of the cycle of the week as well as relative to an event that took place Matthew 12:1 NASB >[a]At that time Jesus went through the grainfields on the Sabbath, and His disciples became hungry and began to pick the heads of grain and eat Luke 6:7 NASB >7 Now the scribes and the Pharisees were watching Him [d]closely to see if He healed on the Sabbath, so that they might find a reason to accuse Him. I picked randomly the above texts but it seems most of them only refer to the Sabbath relative to the events that were taking place. There seems to be no clear instruction to keep the Sabbath in the New Testament. But many churches do teach that Christians are to keep the Sabbath. So what is the Biblical Basis for Christians keeping the Sabbath?