Shortening the beard
Having a beard is becoming more and more accepted. Islam commands Muslim men to grow their beards because this has an important role in the religion.
Is it permissible for the Muslim to shorten his beard if he is ordered to grow it? There are two situations for this.
It is forbidden for the Muslim man to trim his beard if it is shorter than a fist length. For example, it is not allowed to keep a short beard by trimming it regularly.
That is forbidden because the Prophet (ﷺ) ordered to let the beard grow.
The Prophet (ﷺ) said: "Cut the mustache short and let the beard grow." [Sahih al-Bukhari 5893]
There is an exception to the rule. Thus, the Muslim can trim his beard if it exceeds a fist length. That is what the Companions and their students practiced.
Abdullah ibn Umar trimmed his beard when it exceeded a fist's length. [Musannaf Ibn Abi Shaybah #25486]
Abu Hurairah trimmed his beard, if it was more than a fist's length. [Musannaf Ibn Abi Shaybah #25488]
Al-Qaasim (grandson of companion Abu Bakr) took from his beard and mustache. [Musannaf Ibn Abi Shaybah #25485]
Hasan al-Basri said: "They (Companions) allowed to shorten of the beard what exceeds a fist-length." [Musannaf Ibn Abi Shaybah #25484]
Ibrahim an-Nakha'ee said: "They (Companions) took away some of the length and width." [Musannaf Ibn Abi Shaybah #25490]
Also the madhabs were of the opinion that it is permissible to trim of the beard that which exceeds a fist length. Thus, Imam Malik and Imam Ahmad reported this, and Imam Shafi'i's beard length was a fist length.
Imam Malik said: "I believe that one shortens the beard if it is too long. It was narrated from Abdullaah bin Umar and Abu Hurairah -RadhiAllaahu 'anhuma- that they both took from their beards what was more than a handful." [Risalah page 683 of Ibn Abi Zayd al-Qayrawani]
Al-Muzani (student of Imam Shafi'i) described his teacher: "I have never seen anyone with a more beautiful face than Shafi'i. If he took his beard in his hand, his beard would not exceed it. Shafi'i said in a poetry: "Some people think that having a very long beard makes you more noble. That is not from understanding and Taqwa (to believe that)." [Tareekh Dimishq 51/280-281]
Ibn Hani narrated: I asked Abu Abdullah (Imam Ahmad) about a person who removed the hair from his cheeks. He replied, "Take from the beard what exceeds a fist length. Take from the length and from under the throat." I once saw Abu Abdullaah take from his cheeks and under the throat." [Masail (2/151) by Ibn Hani]