In the OT era, it is a law, so it is a must. However, in the NT era, it is not we must give the tithe to GOD, but the way we show our love to God freely. God does not force us, but when we do it we can remember His generious love and mercy, and also to show our love to Him. It is no longer a law, but a way to show the love relationship.
Why we should tithe?
Amen. It’s not a law now, for those who see God’s love, they are willing to give everything to God.
2 Corinthians 9 Each of you should give what you have decided in your heart to give, not reluctantly or under compulsion, for God loves a cheerful giver.