I was reading about how we have to obey the Sabbath rule and observe the Holy Days. But this contradicts this Scripture:
Romans 14:5-6 KJV
One man esteemeth one day above another: another esteemeth every day alike . Let every man be fully persuaded in his own mind.  He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it . He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.
As well as others that say that we are not under the law anymore. Is there a command in the New Testament telling us to observe the Holy Days? What do you guys think? I know that the Word of God is the final authority, and I believe that the answer is no.
That must be what Jesus meant when He said that He was going to fulfill the law.Here is a way of thinking about it that you can consider/evaluate/ask people about:
One of the things revealed through Christ's coming is that the feasts/rituals/sacrifices, etc were done in anticipation of His coming. For example, in the OT, they carried out sacrifices at certain times, like the Day of Atonement, but we live our lives as people whose sins are atoned for by Christ's one sacrifice. They practiced a weekly rest for one day, but we live our lives as people who have found true rest in Christ. In a feast, they remembered when their people had been passed over for death, but we live our whole lives united as a people who have been passed over for death. So the teachings and revelations of Christ don't cancel out the OT laws, but He taught us what those "laws" were really all about the whole time: the hope of His coming. So we don't live our lives as people still hoping and waiting, but as people who have experienced the transforming power of Christ.