The Poem of El Cid takes place during the make or break medieval society of King Alfonso. These were the years of the Reconquering of Spain by the Moors, making the chivalry class of knights essential to the safety and security of the kingdom.
El Mio Cid is supposed to exemplify the medieval soldier: courageous yet vulnerable, strong yet loving, but most importantly, he must be the epitome of the honorable man.
In comes the beard. Spain, influenced by both Muslim and Catholic traditions, follows the tenets of the sacred writings when it comes to roles within the family, as well as society. For centuries, the accepted notion of the beard is from the Apostolic Constitutions which date to circa the year 380 and state,
Men may not destroy the hair of their beards and unnaturally change the form of a man. For the Law says, “You will not deface your beards.” For God the Creator has made this decent for women, but has determined that it is unsuitable for men.
Although El Cid does not necessarily keep his beard only because of this tradition, he also keeps it because his beard is particularly long and bushy. This, again, is a social sign of superiority and manhood. This is also because it used to be a deadly miscue to pull a man's beard. A duel would ensue and someone would have to die as a result. By keeping his beard flowing and long, Cid is placing the dare on the table. If anyone would choose to pull Cid's beard, he would have to accept a duel with El Cid. The fact that El Cid is able to enjoy this freedom with no worries, for nobody dares to duel him, tells a lot about the respect that he enjoys as a knight.