In "Biblical Perspective" Larry Grile writes:
There are perhaps several important things to be said about this passage as well as the general issue of tithing, giving offerings, etc. Tithing was a practice long before the Old Testament Law was given (Gen. 14:20; 28:22). It was enlarged and required under the Sinai Covenant. Still in Jesus' day it was practiced by the adherents of the Law and was commended by Jesus (Matt. 23:23). After the inauguration of the New Covenant at Calvary, no more reference was made to tithing. The concept of tithing is found in only one place where Paul asked the Corinthians to lay aside money according to their financial profit during the week, to be given as an offering on the first day of the week when they gathered together for worship. Since tithing preceded the Law, was commanded as a worthy part of the Law, and was commended by Jesus, it has been generally considered by devout people as a proper way to honor God with our substance. Many have proven God's promise and found Him true to His word. As for offerings, Malachi was referring to special required offerings of animal sacrifices, etc., and to freewill offerings as mentioned in the Law.
Source: Building Christian Relationships: Adult Teacher's Insights, page 35.