“Will a man rob God” is not speaking of robbery in the earthly sense. This phrase is found in Malachi 3:8: “Will a man rob God? Yet you have robbed Me! But you say, ‘In what way have we robbed You?’ In tithes and offerings.” In the law God gave, a system of tithing was set up so that the temple priests, Levites, widows, orphans, and foreigners could be cared for. The tithe would be brought to the temple and then would be distributed to meet the needs for which it was given.
God made tithing universal. A tithe was 10% of one's income. So not everyone gave the same dollar amount, but everyone gave the same percentage. Therefore, by not tithing as they should, they were taking from God’s house, His children, and His servants, thereby robbing God. In response to His question, “Will a man rob God?” God reminded the people that if they would obey, He would bless them for their obedience.
Malachi 3:10 says, “Bring all the tithes into the storehouse, that there may be food in My house, and try Me now in this, says the Lord of hosts, if I will not open for you the windows of heaven and pour out for you such blessing that there will not be room enough to receive it.”
The moral of this passage is, you can do more with 90% and God on your side than you can do with 100% on your own. On pen and paper, tithing may not make much sense, but the miraculous seldom does! So, give tithing a try and see what your faith and His power will do.