Question 9: Any command given by the Messenger of Allaah (peace be upon him) indicates obligation and duty. However, there is a Hadeeth whose apparent meaning contradicts the Hadeeth narrated by ‘Aboo Hurayrah (may Allaah be pleased with him): When I command you to do anything, do of it as much as you possibly can. How can a Muslim reconcile these two Hadeeths?
Answer: The basic rule concerning any commands of the Prophet (peace be upon him) is that they denote obligation, unless otherwise indicated. However, fulfillment of obligation is in accordance with one’s ability, because Allaah (Exalted be He) says: So keep your duty to Allaah and fear Him as much as you can This is also supported by the Hadeeth mentioned in the question… read more here.