“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.” 2 Corinthians 9:7
Bingo.
In Old Testament tithes are spoken of in Malachi Chapter Three.
I would say though, that if people could give 10% under the Old Covenant - a Covenant that Paul the Apostle said in 2 Cor. 3:11 was a transitory one, and one which was superseded by the New Covenant which has a glory that “lasts,” - and an Old Covenant which Paul also said was old, obsolete and ready to vanish away, then why can't NT people (those whom Paul would say are more than able to give 10%) give 10%?
And not give 10% not out of compulsion but out of a cheerful heart?