What exactly is the difference between the ‘Mustahab’ (stressed sunnah) and the ‘Waajib’ (obligatory)?

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.

What is the difference between Sunnah and Fard?

Question 1: People in our country differentiate between Sunnah (supererogatory act of worship following the example of the Prophet) and Fard (obligatory). They say that Allaah’s punishment takes place only when someone leaves the acts that are relevant to Fard or stressed Sunnah. However, I believe that anything which Muhammad (peace be upon him) has done or clarified to his Ummah is an obligation. Accordingly, those who do not do this are considered to be hateful of what Muhammad has come with. Growing the beard for example, has been ordained by Muhammad (peace be upon him), is it authentically proven that he shaved it? Does shaving it imply a sign of hatred to what Muhammad (peace be upon him) has come with? Does whoever does this fall under the same Aayah?

Answer: All Praise be to Allaah Alone and peace and blessings be upon His Messenger, his family and Companions. To proceed: Obligation is what a person is rewarded for doing and punished for abandoning. Sunnah or (the desirable acts) is what a person is rewarded for doing… read more here.