The New covenant and the Old covenant

The holy Bible is composed of the Old and New Testaments. The old Testament means the old covenant and the New Testament is the new covenant. And it is the common opinion among the Christians that the old covenant was abolished through the Cross, and that the new covenant- the New Testament-must be kept. So to accept and observe the teaching of the Old Testament as its face value is the act deserving to be separated from the grace of Christ. Therefore, we have to find the teaching we are to follow in the New Testament, the new covenant.

The standard of all the doctrines is Jesus, who is our teacher and our Lord. All that He has taught and done must be observed as a lesson for us. And we also should follow the examples of the disciples who had been directly taught by Jesus. To ignore their teachings and to add men's opinions to them is heresy. For it is written:
Gal.1/6-9 But even if we or an angel from heaven should preach a gospel other than the one we preached to you, let him be eternally condemned!.... so now I say again: If anybody is preaching to you a gospel other than what you accepted, let him be eternally condemned!"
But as time passed on, the truths began to be changed one by one. As Jesus prophesied that an enemy, the devil, would sow the weed after He sowed the good seed_the gospel of heaven(Matt.13/24-30), the truth of life began to loose its light after the apostolic age: A.D. 167 the Passover was changed to the other day. Vatican who held the supreme power over the church and Dr. Kidd gave a verdict of heresy to those who celebrated the Communion on the fourteenth day of the first month(Nisan)by scared year.
After that, Satan's evil works changed in A.D. 167 and the Sabbath in A.D. 321. But God's truth cannot remain trampled by Satan forever. According to the prophecy, the light of the truth began to appear in its due time. Luther brought to light the freedom of faith, and the Baptist Church baptism, and the Seventh-day Adventist Church the Sabbath. Now there remains one, which is the Communion of the Passover that gives life. We should prepare the way of the Second Coming Jesus and bring to light the last truth- the Passover- and preach it to all who seek the truth of life, that we may be washed away with the blood of Jesus the Passover Lamb and enter the eternal life.

This good news is not a new one, but the gospel taught by Jesus and proclaim by the Apotles. For it is written:

Phil.4/9 whatever you have learned or received or heard from me, or seen in me- put it into practice. and the God of peace will be with you.

1 Cor. 11/23-26 For I received from the Lord what I also passed on to you: The Lord Jesus, on the night he was betrayed, took bread, and when he had given thanks, he broke it and said, "This is my body, which is for you:do this remembrance of me." In the same way, after supper the took the cup, saying, "This cup is the new covenant in my blood: do this, whenever you drink it, in remembrance of me." For whenever you eat this bread and drink this cup, you proclaim the Lord's death until he comes (cf Luke 22/7~20)

The Passover is the core of the new covenant. Jesus and Apostle Paul called the Passover the new covenant.

https://youtu.be/0byKtzaCm0M