The third pillar of Islam is charity for members of the community.  This is an explicit requirement for members of Muslim communities to support each other.  Membership in a Muslim community is implied.
In our case, membership in a religious community not implied, so we must explicitly require 
joining a religious community.  For those following the Old Testament under Islam, this means taking part in a local mosque.  Financially supporting the mosque is strongly encouraged.
I currently attend my local mosque twice a week, at Jumah (Friday prayer at 1:30pm) and Saturday night (Magrib and Isha prayers).  This works well with a Saturday sabbath because these times bracket the sabbath.  Effectively I have my weekend on Friday and Saturday.