One reason the Lord illustrates doctrines with the most extreme circumstances is to eliminate excuses. If the Lord expects even the poorest widow to pay her mite, where does that leave all others who find that it is not convenient or easy to sacrifice?
No bishop, no missionary should ever hesitate or lack the faith to teach the law of tithing to the poor. The sentiment of “They can’t afford to” needs to be replaced with “They can’t afford not to.”
One of the first things a bishop must do to help the needy is ask them to pay their tithing. Like the widow, if a destitute family is faced with the decision of paying their tithing or eating, they should pay their tithing. The bishop can help them with their food and other basic needs until they become self-reliant.... the most important assistance comes from God, not from man. The prophet wanted to help them unlock the windows of heaven as promised by the Lord in the book of Malachi (see Mal. 3:10; Mosiah 2:24).
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When serving a meal, it is much easier to set one more plate at the beginning of the meal than it is to find food for a latecomer once the meal is over and the food has been served. Likewise, isn’t it actually easier to give the Lord the firstlings or the firstfruits than it is to hope that there are sufficient “leftovers” for Him? As the founder of our feast, shouldn’tHe be the guest of honor, the first to be served?April 2005 :Tithing—A Commandment Even For The Destitute" Lynn G. Robbins