This pericope begins with the affirmation that God is unchanging in his loving care of Israel. God's steadfast love (cf. Hos 2:19-20rsv) is the expression of his fidelity to the covenant made with his people. He expects the same kind of devoted loyalty from Israel. Instead they have been consistent in their stubborn turning away from Yahweh's decrees. Nothing can rectify such waywardness except returning to God. There is in this contrast of consistencies the graphic picture of the primary meaning of sin and repentance. Sin is departure from God. Repentance is returning to him.
The people's inquiry as to how they are to return—a question indicating that they are insensitive to the fact of their departure—gives the prophet an opportunity to be specific. They have actually robbed, or cheated, God of that which is due him. Tithes and offerings have been withheld on a nationwide scale (cf. Ne 13:10-13). This is the cause of their poverty (v. 9). The antidote for the “curse” upon them is to be faithful in the gifts required by the law (Lev 27:30; Nu 18:21-24; Dt 12:6, 7, 11-14). Their prosperity, if they are faithful in their obligations to God, will become known throughout the world, giving them a reputation of living in a delightful land (v. 12).
The emphasis on material blessings should not be construed to mean that the prophet was concerned only with external matters either in worship or in the blessings of God, although the time of the prophet may well mark the point in history where such an emphasis began to be made. The Deuteronomic theory linking righteousness with blessings and sin with curses was deeply embedded in the theology of this day. Malachi may well have realized that material prosperity does not always accompany right conduct, but he was sure that the total well-being of Israel was dependent on their faithfulness to God in all of their relationships. The law of the Sabbath is expanded into the need to keep every day holy. In the NT the priesthood is expanded from one tribe, the Levites, to include all of God's people (cf. 1Pe 2:5, 9). The concept of the tithe is enlarged to include faithful stewardship of all resources. Everything belongs to God (Verhoef, 311).