Lev 19:18
Here's the deal.
A lot of the laws were specifically to do with Israel's theocracy and sacrificial system. The book of Hebrews spends a lot of time telling the Christian not to try to return to that. Because of Christ, that sacrificial system is no longer valid. It was a type pointing forward to Christ, and He fulfilled it.
(By the way... One should research the tithe, who it was given to and why... It was specifically stated that it was given to Israel to support priests because they got no share in the land. Paul ignored it when he taught Christian giving, which is specifically not to be a matter of compulsion but instead a matter of the heart, and was to be as much as the Holy Spirit tells one to give--not a predefined amount. The church is not Israel, there are no priests, and a Christian should give as a matter of heartfelt worship. I say this as a pastor. lol)
A lot of the law was an ethical treatise which carries over. The problem was that Israel had interpreted these parts as something that made them righteous, and used them as an outer show to gain religious glory.
Jesus pointed out that we are in desperate need of His righteousness. That ethic is completely fulfilled by loving God and loving everyone else.
For instance, Israel had interpreted the law "an eye for an eye..." as a guarantee of vengeance--to get your pound of flesh. But it was given out of love and protection to ensure against vengeance--to ensure that the punishment would not be overly severe.
Instead, to fulfill the law turn the other cheek.
Israel thought they could be holy by keeping the law as external actions. Jesus said no one can keep the law without a redeemed heart and the actions of the Holy Spirit within. So, the law is alive and well as an ethic that Christ seeks to live out through love in His followers.
It's an oxymoron. Fulfill the law through love for God and others, not by trying to keep the law. It's something that happens on the inside, not something you do on the outside.
So, to return also to the tithe--you keep it's 'spirit' by loving God, not by legalistically counting percentages as if God is a waiter and you're giving him a tip.
Sorry for the length.