The entire Book of Hebrews speaks of the old sacrificial system and how it really pointed to Jesus and his death on the cross. Since Jesus hadhas paid the price once and for all time, no more blood sacrifices are necessary.
The Apostle Paul also spoke to the issue of celebrating the Jewish holidays, saying that they were not obligatory. In Galatians 4 he says:
8 Formerly, when you did not know God, you were slaves to those who by nature are not gods. 9 But now that you know God—or rather are known by God—how is it that you are turning back to those weak and miserable forces[d]? Do you wish to be enslaved by them all over again? 10 You are observing special days and months and seasons and years! 11 I fear for you, that somehow I have wasted my efforts on you.
And in Romans 14, Paul says:
5 One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. 6 Whoever regards one day as special does so to the Lord.
This still leaves many parts of the Old Testament Law that were never rescinded nor commanded. Christians have been debating those rules ever since. However, if you read the New Testament carefully, you will at least find that the Ten Commandments are all still in force, since at one point or another all of them are covered.
However, even those commandments that are still in force are to be looked at in a new light. You are not justified by following them. Instead, having trusted in Christ by faith, as a saved person under the instruction of the Holy Spirit, you will desire to follow them out of love.