I am a young man in my early twenties. Is it obligatory in Islam to grow my beard? If yes, what is the appropriate length of the beard?

There is scholarly difference over keeping a beard

From the matters that are confirmed throughout Islamic law is that keeping of the beard and refraining from shaving it are from the acts of the Prophet (peace and blessings be upon him). He used to trim his beard and trim its sides and top portions in order to match the contour of his face. He also used to wash his beard with water and comb it.

It is also known that the Companions of the Prophet emulated his actions and decisions. There are Prophetic texts that support keeping and maintaining the beard just as there are texts that support the use of the toothstick (siwak) and cutting one’s nails and mustache.

Some of the jurists have taken these texts to mean that these actions are obligatory, and according to this opinion, shaving the beard would be prohibited. Other jurists have taken these texts to mean that these actions are recommended, and according to this opinion, keeping of the beard is a sunnah; one is rewarded for keeping it and not punished for leaving it.

As for the first opinion that prohibits shaving the beard, the text proofs used are the ones encouraging Muslims to grow their beards to distinguish themselves from disbelievers. Imam Muslim reported on the authority of `Aisha, that the Prophet (peace and blessings be upon him) said, "Ten things are from the primordial state (fitra): clipping the mustache, keeping the beard, using the toothstick, snuffing water and expelling it from the nose to clean it, trimming the nails, cleaning the knuckles, plucking out underarm hair, shaving pubic hair, and decreasing the amount of water used." Some of the narrators said, "and I forgot the tenth, which is rinsing the mouth with water."

As for the second opinion, it is the opinion of Shafi’i scholars who maintain that shaving the beard is not prohibited. They based their opinion on their understanding of the command related to customs, food, drink, clothing, sitting, etc. which is understood to be a recommendation and not an obligation. They used the examples of the command to dye clothes and to pray in sandals to prove that these are not commands imposing obligation, but rather recommendation as Ibn Hajr al-`Asqlani mentions in his commentary on Sahih Bukhari.

As mentioned above, the Prophet (peace and blessings be upon him) used to trim his beard and clip its sides. Some scholars permit trimming off the hair of the beard that exceeds the amount that may be grasped in the fist because this was the practice of Ibn ‘Umar. The most important thing about keeping a beard is to maintain good appearance so as not to give a bad impression about Muslims.

Based on this, it is clear that there is a legitimate scholarly debate concerning the ruling of keeping the beard. When there is a scholarly difference of opinion concerning a certain issue, it is preferable to avoid it. But if this is not possible, Muslims are to follow the scholars who permit it. Therefore, it is permissible to keep a beard, but it is not an obligation, and let it grow to fist length following the example of Ibn 'Umar.