Ibrahim An Nakha’i (rahimahullah) said: “They [The Sahabah radiyallahu ‘anhum] used to trim their beards on the sides.” (Sharhus Sunnah).
Imam Bayhaqi (rahimahullah) has recorded this narration with an acceptable chain. The full narration is as follows:
Ibrahim An Nakha’i (rahimahullah) said: “The [Sahabah radiyallahu ‘anhum] would trim from the sides [of the beard, the hair exceeding one fist] and clean it, i.e. The beard.”
(Shu’abul Iman, Hadith: 6018. Also see: Sharhus Sunnah, vol.12 pg. 108/109, under Hadith: 3194)
Also see here.
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar