First, we must say that there are two themes in this question that are difficult to combine. That is to provide precise jurisprudential arguments in simple words that are understandable to laity. In fact, in order for a person to understand jurisprudential issues completely, one has to complete different stages of knowledge since he cannot grasp a jurisprudential demonstration concerning an issue unless he acquires the preliminaries. This same reason has led people to divide into followers and Mujtahids. However, we can briefly present some of the arguments in this connection and, if you yourself fail to attain the degree of Ijtehad, you should not embark on inferring and deducing from them; rather you should, in this regard, follow qualified Mujtahideen (jurisprudents) or religious authorities.
Another point that must be taken into consideration is that, exercising precaution in dubious and doubtful matters, as the Holy Prophet (pbuh) said, is better and easier than to get bogged in a quagmire of destruction.[1]
Keeping in view the above narration and the fact that in today’s life it is not possible to have direct access to the Infallible Leaders (a.s.) whom we could refer to and ask our questions in order to obtain and learn divine laws and their reasons, religious scholars have underscored the importance of exercising precaution in issues that are not backed by strong, indisputable and convincing proofs but are loosely or remotely connected to sporadic arguments. Thus, they consider exercising precaution to be a reliable method in matters in which precaution does not inflict serious damage on one’s routine life and that it does not also lead to extreme and unbearable difficulty and hardship.
We also act in the same manner in similar circumstances. For instance, if we are planning to go on a journey and there are two roads which we can use to reach our destination but one of the roads is insecure and risky because of the possibility of landslides, presence of thieves, dacoits and robbers but the other road is secure and there are no such dangers, obviously we choose the second road even though it might be longer and more unsmooth.
Having said that, we will now mention some of the reasons that are used or relied upon in connection with this juridical rule:
1- There is a verse in the Quran according to which changing Allah’s original creation is a satanic act.[2] It has been argued in some jurisprudential discussions that since God has made beard as part of all men’s creation, therefore, shaving and removing beard is tantamount to altering Allah’s creation which has been forbidden by the verse. The conclusion is that we should not do such an action.
2- There are many traditions from the Holy Prophet (pbuh) and Infallible Imams (a.s.) forbidding Muslims from shaving beard. According to some of those narrations, this act causes Muslims to look like unbelievers. For instance, the Holy Prophet of Islam (pbuh) says: “Trim short your moustache and keep your beard long (to some extent) so as not to look like Majusids.”[3] Also, Imam Reza (a.s.) was asked about permissibility of shaving beard in response to which, the Imam (a.s.) said. “There is no objection to shaving the hair on your cheeks but you should not shave the front part of your beard.”[4] Of course, it is worth notice that on the other hand keeping very long beard has been discouraged.[5]
3- Another reason presented in this regard is that although some jurisprudents have not issued an explicit fatwa on prohibition of shaving beard and they have simply recommended precaution, no jurisprudent has been witnessed over the centuries to give a fatwa on permissibility of shaving beard. This indicates that religious scholars are unanimous in this regard.
4- If we study the life as well as descriptions of the appearance and complexions of religious leaders, nobles and pious people, we will not find a prominent religious personality who may have shaved his beard. This is by itself evidence indicating that shaving beard is not considered a favored act in Muslims’ common sense.
In any case, the above reasons over and above to other reasons, have been mentioned and expiated upon in demonstrative jurisprudential books. There are books printed and published that deal with and specifically substantiate prohibition of shaving beard.[6] On the other hand, other prominent scholars have considered the foregoing arguments to be weak and unconvincing. They have said that these arguments cannot be used to issue an explicit fatwa on prohibition of shaving beard.[7] However, all of them agree that the best way in regard to this subject about which there exist discrepancies and discordance is to observe precaution by not shaving beard. Even if the reasons and proofs which prohibit shaving beard may not be complete and credible, we are certain that there is no problem in keeping beard of an ordinary size. If we can keep beard when there is no serious problem facing us, we can be sure that we have not violated Islamic doctrines. If that is the case, why should we shave our beard when it is likely that shaving might be an act of disobedience and violation of Islamic laws?! Hence, given the saying of the Holy Prophet (pbuh) who advised to adopt precaution in doubtful matters, keeping beard of an ordinary and regular size is the best way to choose.
Finally, it should be noted that not shaving beard does not mean negligence towards cleanliness or tidiness of the beard; rather, as the Holy Prophet (pbuh) said, everyone should look after his hair.[8] There is a chapter in textual sources about keeping the beard tidy and clean.[9] In this regard, there are more details in questions 20900 and 2123 on our website. You can refer to these questions, if you wish to.

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