Some of the rules in the Old Testament are no longer applicable today. So what lessons can we get from them? Is the Old Testament still relevant to us?
The Old Testament is definitely relevant to us, and who said that the Old Testament rules are not applicable today? Our Lord Jesus Christ said, "Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill" (Matthew 5:17). The Old Testament has some symbolic allusions and practices that were fulfilled in the New Testament. That is why we do not revert to them.
For example circumcision is a symbol for baptism. We no longer practice circumcision because it has been replaced by its antitype, baptism (Colossians 2:11-12). It says in Colossians 3: 9-10, "You have put off the old man with his deeds, and have put on the new man, who is renewed in knowledge according to the image of Him who created him." We can not understand baptism in its concept except through its type (symbol) which is circumcision.
Also, the Old Testament various sacrifices, for example, the burned offering and the thanksgiving sacrifices were offered to honor God, and to reconcile us with Him. They were a type of a sin carrying cross. Now, we do not offer sacrifices because we have the antitype which is the communion and the Eucharist.
So, although we do not literally practice the Old Testament rituals; yet they shed light on their New Testament antitype.