All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
As for shaving the beard, it is forbidden according to the Hanafi, Maaliki, and Hanbali schools of jurisprudence, as well as most later scholars of the Shaafi'i school of jurisprudence.
On the other hand, most scholars believe that it is permissible and not disliked to cut off what exceeds one's fist of the beard hair. The same opinion is reported from Ibn Abu Shaybah in his Musannaf from ‘Ali Ibn Abu Taalib, Abu Hurayrah, ‘Abdullah Ibn 'Umar Ibn al-Khattab, Taawoos and al-Qaasim Ibn Muhammad Ibn Abu Bakr. Jabir said: 'We do not shorten our beards except in Hajj or ‘Umrah.”
In al-Muntaqa, Malik was asked: 'What to do if one's beard becomes too long?' He replied: 'I think it is better to trim it.”
Ibn Mufleh in al-Aadaab ash-Shar'iyyah said: 'It is Sunnah to let one's beard grow. It is said: to the extent of one's fist. This means that one can trim what exceeds one's fist or leave it; but it is better to leave it.”
In brief, there is disagreement among the scholars concerning the definition of "letting the beard to grow". Some scholars believe to let it grow to become long without any form of trimming. Others say there is no objection to cut off what exceeds one's fist. But, it is known that the Sunnah of the Prophet is to completely avoid any form of trimming.
For more benefit on keeping the beard, please refer to Fataawa 332320, 317029, 119302, and 91108.
Allah knows best.