Albert Barnes Commentary Malachi 3:8

"Will a man rob God? yet ye rob me. But ye say, Wherein have we robbed thee? In tithes and offerings." — Malachi 3:8 (ASV)

Will a man rob or cheat—defraud God? God answers question by question, but thereby drives it home to the sinner’s soul, and appeals to his conscience. The conscience is steeled, and answers again, “In what?” God specifies two things only, obvious, patent, which, as being material things, they could not deny. “In tithes and offerings.” The offerings included several classes of dues to God:

• The firstfruits;
• The annual half-shekel (Exodus 30:13–15);
• The offerings made for the tabernacle (Exodus 25:2–3; Exodus 35:5, 21, 24; Exodus 36:3, 6) and the second temple (Ezra 8:25) at its first erection; it is used of ordinary offerings;
• The tithes of their own tithes, which the Levites paid to the priests (Numbers 18:26, 28-29);
• The portions of the sacrifice which accrued to the priests (Leviticus 7:14).