The truth is that, thiting is not only the old testament issue, it is also been commanded in the new testament by Jesus christ in matthew 23 v 23 . "woe unto you, scribes and pharisees, hyprocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgement,mercy,and faith:these ought you to do,not leave the other undone.(NOTE: and not leave the other undone i.e not undo thiting.)
One additional important point I will like to make is tthat thiting is for the payer advantage, it is not a compulsion,it is a covenant between God and man. God covenanted that when we do it we shall be bless and devourer shall be rebuke for our sake.However any body that think it is only for the isrealits or the levits should not also claime some blessing in the old testament e.g call upon me and I will answere you, no weapon formed aginst me shall prosper e. t . c. I think why most of us regret of paying tithe or why we are not been bless when we pay our thite is because of the place( the church) we pay it. their is always a divine appointed place to pay thite and offering if we want to be bless. it now depend upon us to locate that appointed places. what I mean by appoited places are churches being pastor by God appointed servants and not exploiter so call pastors.
Hence thiting is not only old testament issue.