Giving tithes and offerings over and over again, year after year is useless.
Why is it repeated?
Because sacrifices done under the old system are repeated again and again, year after year, but even though they can never save those who live under their rule.
“For the law having a shadow of good things to come, and not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect.” Hebrews 10:1
Ask yourself, after giving and you have done all those sacrifices you do, why you feel it’s not enough, you need to do more?
It’s because you live under a rule, a principle that subdues or controls those under it that they should always feel guilty and want to do more. Hebrews 10:3 says, “But in those sacrifices there is a remembrance again made of sins every year.” So you should not cease to offer. You are ever ready; every hour, everyday, every month and year after year, to spend and got spent. Alive in you is the conscience of sins.
But the true plan is “…the worshippers once purged should have no more conscience of sins.” (Hebrews 10:2).
“Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me:” Hebrews 10:5
Does this only refer to those sacrifices which they did year after, i.e., the offering of animals?
No, but to everything that concerned the old system. “Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.  By the which will we are sanctified through the offering of the body of Jesus Christ once for all.” Hebrews 10:9-10
God has no pleasure in sacrifices and offerings, no matter what that is.
“But this man [Jesus], after he had offered one sacrifice for sins for ever, sat down on the right hand of God.” Hebrews 10:12
Hebrews 10:14-18 says,
 For by one offering he hath perfected for ever them that are sanctified.  Whereof the Holy Ghost also is a witness to us: for after that he had said before,  This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them;  And their sins and iniquities will I remember no more.  Now where remission of these is, there is no more offering for sin.
He came, died and arose that you should have no more conscience of sins.
The blood of the covenant
Hebrews 10:26,28-29 says,
 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,  He that despised Moses’ law died without mercy under two or three witnesses:  Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
“Cast not away therefore your confidence, which hath great recompence of reward.  For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.” Hebrews 10:35-36