To keep beard equal to one fist in length is not just Sunnah, but it is Wajib (Mandatory).
To shave beard or trim it less than one fist length is HARAM (strictly prohibited).
(Behisti Zewar, Chapter 11, Page 115)

Beard should be of one’s own fist length from all three sides (right, left and below the chin)

Maulana Shah Hakeem Muhammad Akhtar Saheb

Published By: Khanqah Imdadia Ashrafia, Gulshan-e-Iqbal, Karachi, Pakistan

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