It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Take from this and leave this" - meaning that (a man) should take from his chin tuft (the hair below the lower lip) and leave his beard.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13419