August 5

As regards the questions about the proper use of the Long Obligatory Prayer: All the writings of the Faith may be read and should be read for the instruction and inspiration of the friends. This includes the specific prayers. If a believer is physically incapable of performing the genuflexions accompanying one of the prayers, and yet he longs to say it as an obligatory prayer, then he may do so. By physically incapable is meant a real physical incapacity which a physician would attest as genuine. 
- Shoghi Effendi  (From a letter dated 17 February 1955 written on behalf of Shoghi Effendi to a Local Spiritual Assembly; included in a compilation: ‘Exemption from Obligatory Prayer’, prepared by the Research Department of the Universal House of Justice)