I just wanted
to get some expert clarification regarding someone with short beard leading salah as
an imam (temporary when the regular imam is on day off)

An Alim is stating it’s not allowed to lead salah if he has a short beard! He’s saying
there’s lots of Dalil and wanted to see if there’s any evidence to suggest such
claim (salah being void behind someone with short beard)!

Answer: 

Nabi Sallallahu Alaihi Wasallam said:

" انَْْكُوا الشَّوَارِبَ، وَ اعْفُوا الل حَى "

"Cut the moustaches short and leave the beard (as it is). (Bukhari # 5893) 

Primarily, to trim or shorten the beard less than the obligatory extent is impermissible in Shariah and the doer is classified as a Fasiq (transgressor). (Qamoosul Fiqh Pg. 582). Moreover, the Imamat of an open transgressor is highly disliked in Shariah. Nonetheless, the Salah will be valid and counted. (Shaami Vol. 1 Pg. 522-531) 

Besides this, to appoint such an Imam who openly commits sins is highly disliked in Shariah. Therefore, the committee members should endeavour to stipulate a befitting Imam. Despite having befitting Imams and the means to hire them, they fail to arrange a befitting Imam, they will be held accountable in the court of Allah Ta'aala. (Fataawa Mahmudiyyah Vol. 10 Pg. 134) 

Furthermore, the above ruling is concerning such individuals who trim and shorten their beards; however, if the beard does not grow long or does not grow at all, in these cases, the ruling will differ and the Imamat of such a person will be sound and valid without any abomination. (Fataawa Mahmudiyyah Vol. 10 Pg. 138) 

ANSWERED BY: MOHSIN KHAN 

CHECKED AND APPROVED BY: Mufti Muhammed Saeed Motara Saheb D.B. 

Islamic Date: ٤ محرم ١٤٤١ 

English Date: 4 September 2019