All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
  is His slave and Messenger.
What is narrated from Ibn 'Umar 
  is sound that when he performed Hajj and shaved his head, he used to trim from his beard what exceeded the length of a fist.
Imaam Maalik 
  reported that when Ibn 'Umar 
  shaved his head after Hajj, he used to trim his beard and mustache.
Trimming what exceeded the length of a fist is also proved, through a good chain, from Abu Hurayrah 
.
Ibn Hajar 
  reported from Jaabir 
  that he said:  "We used to let the beard grow except in Hajj and 'Umrah."
Ibn Hajar 
  reconciled between the narration of Ibn 'Umar 
  and his action, as he said: "It seems that his act of trimming the beard was not limited only to the time of Hajj or 'Umrah, rather he understood that the command of growing beard is restricted only if the beard does not deface one's face by extra length or width."
Allaah Knows best.