Surah at-Taghabun (The Deprivation) 64 : 16

Explanatory Note

The believers are admonished to do their best to remain God-fearing and to obey God's orders. Here we see an aspect of God's care as He restricts what is expected of the believers to that which remains within their power and ability. He knows the limit of what they can do in obedience of Him. The Prophet says: "When I give you an order, do it as best you can, and when I prohibit something, refrain from it completely." [Related by al-Bukhari and Muslim.]

Limits cannot be set on obeying an order to do something. Therefore, what is within one's ability and power is sufficient. On the other hand, prohibition cannot be divided. It is required in full.

They are also called upon to be generous in what they donate: "And be charitable. That will be best for you."  Normally, they spend their money on their own needs. God instructs them to spend in charity what is good for themselves. Thus, when they are charitable, they are actually spending their money on what is good for themselves. The surah also depicts meanness as a plague, one they must try to get rid of.