malachi 3:8 Will a man rob God? Yet ye have robbed me. But ye say, Wherein have we robbed thee? In tithes and offerings. - Free Bible Online

      8. rob--literally, "cover": hence, defraud. Do ye call defrauding God no sin to be "returned" from (Mal 3:7)? Yet ye have done so to Me in respect to the tithes due to Me, namely, the tenth of all the remainder after the first-fruits were paid, which tenth was paid to the Levites for their support (Le 27:30-33): a tenth paid by the Levites to the priests (Nu 18:26-28): a second tenth paid by the people for the entertainment of the Levites, and their own families, at the tabernacle (De 12:18): another tithe every third year for the poor, &c. (De 14:28, 29).
      offerings--the first-fruits, not less than one-sixtieth part of the corn, wine, and oil (De 18:4; Ne 13:10, 12). The priests had this perquisite also, the tenth of the tithes which were the Levites perquisite. But they appropriated all the tithes, robbing the Levites of their due nine-tenths; as they did also, according to JOSEPHUS, before the destruction of Jerusalem by Titus. Thus doubly God was defrauded, the priests not discharging aright their sacrificial duties, and robbing God of the services of the Levites, who were driven away by destitution [GROTIUS].

JFB.