"Fools and blind! For which is greater, the gold or the temple that sanctifies the gold? [...] Fools and blind! For which is greater, the gift or the altar that sanctifies the gift?" Matthew 23.17-19Tithes and offerings carry a revelation in itself: what is in the offering giver's heart.
Firstfruits show faithfulness and offerings reveal love.
While there was no sin in the world, tithes and offerings were not necessary, since the communion between the creature and the Creator was perfect. With sin came the moral and spiritual corruption. Therefore, God established the tithe and offerings to prove the heart of those who approached Him.