cat /etc/fonts/conf.d/65-fonts-arabic.conf 
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
         <alias>
                 <family>sans-serif</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>
         <alias>
                 <family>Comic Sans MS</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>
         <alias>
                 <family>sans</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>
         <alias>
                 <family>Trebuchet MS</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>

         <alias>
                 <family>serif</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>

         <alias>
                 <family>courier</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>
         <alias>
                 <family>monospace</family>
                 <prefer>
                         <family>almateen</family>
                 </prefer>
         </alias>
</fontconfig>