Salāt al-jumu‘ah, “Friday prayer”, is a congregational prayer that Muslims hold every Friday, just after noon instead of the Dhuhr “noon prayer” which is the prayer after midday. Unlike other prayers which can be done anywhere Salāt al-jumu‘ahis conducted in mosques and Muslims are expected to attend and it as documented in the Quran.
“O ye who believe! When the call is proclaimed to prayer on Friday (the day of assembly) hastens earnestly to the Remembrance of Allah and leave off business (and traffic): that is best for you if ye but knew! “
To leave any and all worldly pursuits and earnestly attend the Friday mid-day sermon and congregational prayer is an absolutely obligatory command of the Allah upon those who have professed belief in Him.
Violent extremists and terrorist like Al shabaab militia claim to be Muslims yet they do not perform basic Muslim requirements like the Salāt al-jumu‘ah. Al shabaab camps are normally in hidden places like dense forests hence they cannot access mosques on Fridays to perform the congregational prayers which Muslims are obliged to.
Furthermore, they are afraid of leaving their camps due to the fear of being captured or killed by the security forces. That is just a clear indication that they are not true Muslims and are just hiding behind religion while tainting the name of Islam.
In addition to all the above they carry out attacks on Friday instead of holding the day dear and respecting it as required by the Quran.
The Friday prayer is of great importance to Muslims and one should endeavour to participate. A Muslim should, therefore, never attempt to miss it. To miss even one Jumu’ah prayer without a legally valid excuse is highly sinful, and to miss three is totally unacceptable. Since they do not practice the basics of Islam we can conclude that terrorists are not Muslims.