What does Malachi 3:10 mean?
This is one of the more popular Scriptures cited by the so-called "Prosperity Gospel," despite it having no bearing on a modern believer. As with verses 8 and 9, this entire discussion is directed at Israel, and within the context of the covenant between God and that nation. Those promises are still in effect, but they apply in literal terms only to those under that covenant: Israel. This verse, in no sense, implies a guarantee from God that those who donate to His cause will be materially blessed. The general principle is sound: we ought to work for the will of God rather than for our own ends (Matthew 6:19–20; 2 Corinthians 9:6–12). However, God does not guarantee wealth or success to the Christian believer, under any circumstances.This promise reflects back to Deuteronomy 28. In that passage, God describes a series of blessings (for obedience) and curses (for failure) tied to Israel's faithfulness to their covenant with Him. Ancient agriculture was particularly vulnerable to insects and other natural dangers; so the pledge made over verses 10 and 11 seems to relate specifically to keeping such harms at bay.
The "storehouse" most likely means a particular area of the temple used to house tithed grain and other resources (Nehemiah 10:38).