Silsilah as-Sahihah 1991 — Growing the beard, trimming the mustache

Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Magians were mentioned in the presence of the Messenger of Allah (peace and blessings be upon him). The Prophet (peace and blessings be upon him) said: "These (Magians) let their mustaches grow and shave their beards, so you should oppose them." Thus, Sayyiduna Ibn Umar (may Allah be pleased with them both) used to trim his mustache in such a way as the hair of a goat or camel is trimmed.