"Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven." Matt 5:17-20
During his earthly ministry, Jesus)p) told his hearers to obey sacrificial aspects of the Law of Moses(p) (Matthew 5:23-24). He told a man he healed of leprosy: "Go, show yourself to the priest and offer the sacrifices that Moses commanded for your cleansing" (Luke 5:14). If the animal sacrifices are the only part of the Law of Moses(p) that are "done away," as some believe, then that idea contradicts Jesus’ actions and teachings—if we assume that we must follow his example in this area. Jesus(p) did not tell people to stop sacrificing. In fact, as the Scripture in Luke shows, Jesus(p) told people to offer the appropriate Mosaic sacrifice. But does this mean Christians should do so? The Answer would be Yes if they are really ''Christians'' Followers of Christ.
Let’s continue with that line of thought. Jesus(p) worshipped at and upheld the sanctity of the temple (Matthew 12-13; Mark 11:15-17). He told his disciples and the Jewish people to obey the teachers of the law and the Pharisees, who sat "in Moses(p) seat" (Matthew 23:1). What would these individuals have instructed people to obey? They would have taught obedience to the entire Law of Moses(p), as they understood it. But must Christians keep the Law of Moses(p) because Jesus(p) told people to do so.. you make the decision off-course.
Jesus(p) was circumcised according to the Law (Luke 2:21). His parents kept the precepts of the Law of Moses(p), including the purification rites (Luke 2:22-24, 39). Jesus(p) kept the old covenant Passover from his early childhood and throughout his life (Luke 2:41-42; 22:11). He kept the annual festivals and other traditional Jewish festivals (John 7:2-10; 10:22).
To summarize, during his lifetime Jesus(p) commanded sacrifices, obedience to the religious leaders who taught all of the Law of Moses(p), and temple worship, with all that this entailed. In short, by his example and words Jesus(p) taught obedience to the ritual laws of Moses(p). We cannot assume that Christians nowadays are real Christians.
Are Jesus(p) remarks or practices regarding the Sabbath or annual festivals proof that Christians must keep these days as holy time? I would say yes since the term still means ''Follower of Christ'', Christians would be obliged to offer sacrifices, participate in temple worship and follow those who taught obedience to the Law of Moses(p). Christian men would also have to be circumcised for religious reasons because Jesus(p) was circumcised (Luke 2:21). Christian women would have to fulfil the specified Mosaic rites of purification after childbirth.
In short, if we say that Jesus(p) remarks in the Gospels are proof that Christians must keep the Mosaic Sabbath or annual festival regulations, then we must accept all of the commands of the Law of Moses as being binding upon us (Galatians 3:10).