In "God's Word for Today" Gordon Snider writes:

[Malachi 3:10-12] focus on blessings that will come to those who honor their financial commitments to God. These verses have been used by preachers of a “prosperity gospel” to prove that it is God's will for His people to be materially blessed. How do the blessings of these verses relate to New Testament Christians?

Source: Building Christian Relationships: Adult Teacher's Insights, page 35.