The context of
Malachi 3:9 is not comparable to our modern NT circumstance.
-We have no Levitical priesthood who are forbidden to own land or property who need the tithe to survive.
-We have no temple.
-The tithes are to be produce, grain, and livestock.
-The tithes collected are not used in accordance to the Law of Moses with regards to the "storehouse" for the poor.
-The tithe isn't binding upon the entire nation.
This system doesn't exist. Therefore, one cannot sin against it.
Now, this isn't to say that we shouldn't support the ministry or the work of the Lord. In fact, it frees us to be far more generous when able, and for those who cannot afford a tithe to give as able.
I believe that the NT presents us with a better option which I've heard called, "Grace Giving". This model of giving is composed of free will offerings and vows (pledges).
I believe "grace giving" becomes superior to tithing. In "grace giving", not only do individuals give voluntary offerings as led when the needs of the church are brought before the body, but individuals can prayerfully "vow" (or pledge) to give so much per check. This can be a percentage of their check, or even a certain amount over a period of time (for example pledging to give $3000 over a year's time). This way the church can make financial forecasts, etc. In this way a responsibility to give is established, but what to give is decided in the heart of the individual.
Can an individual choose to give 10%? Certainly! But this isn't a legalistic mandate with the threat of hellfire attached to it. In fact, families of more meager income can pledge a lower percentage or amount. And those of greater income can give as much as 90% of their income should they desire. None are shut out and all are blessed by giving. The widow and her mite isn't denied full fellowship because she can't afford to both tithe and pay for her medications.
Paul wrote that hose who give bountifully will reap a bountiful reward. Those who give sparingly will receive sparingly...
2 Corinthians 9:6-10 English Standard Version (ESV)
6 The point is this: whoever sows sparingly will also reap sparingly, and whoever sows bountifully will also reap bountifully. 7 Each one must give as he has decided in his heart, not reluctantly or under compulsion, for God loves a cheerful giver. 8 And God is able to make all grace abound to you, so that having all sufficiency in all things at all times, you may abound in every good work. 9 As it is written,
“He has distributed freely, he has given to the poor;
his righteousness endures forever.”
10 He who supplies seed to the sower and bread for food will supply and multiply your seed for sowing and increase the harvest of your righteousness.
So, the principle of blessing in accordance to sacrifice does apply.
Most multi-million dollar charities and non-profit organizations function this way. Also, most television and radio ministries function this way. And most are more successful (statistically speaking) in maintaining their operations than the average church start-up.
This is why I am an advocate for "grace giving".