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Source:Robert D. Hales:The Divine Law of Tithing:The First Presidency has written what the law of tithing is for us today
Robert D. Hales: "The First Presidency has written what the law of tithing is for us today"
Elder Robert D. Hales:
The First Presidency has written what the law of tithing is for us today: “The simplest statement we know of is the statement of the Lord himself, namely, that the members of the Church should pay ‘one tenth of all their interest annually,’ which is understood to mean income. No one is justified in making any other statement than this.” (First Presidency letter, 19 March 1970.) 
- Robert D. Hales, "The Divine Law of Tithing," Ensign, March 1970