Notes On Obligatory Prayers And Ablutions compiled by Research Department of the Universal House of Justice in a letter to an individual fm the House of Justice 15 April 1987 As Appeared In Baha'i Studies Bulletin Vol. 4:3-4 2 January 1991
The instructions that accompany these prayers, such as the washing of hands and face, of bowing down and of raising one's hands, have been definitely ordained by Bahá’u’lláh, and as such should be entirely and confidently carried out by the believers, and particularly by the Bahá’í youth on whose shoulders has been laid the chief responsibility of vindicating the truth, and preserving the integrity of the laws and ordinances of the Faith.
The daily obligatory prayers are three in number. The shortest one consists of a single verse which has to be recited once every twenty-four hours and at mid-day. The medium which begins with the words "The Lord is witness that there is none other God but He" has to be recited three times a day, in the morning, at noon and in the evening. This prayer is accompanied by certain physical acts and gestures. The long prayer, which is the most elaborate of the three, has to be recited only once in every twenty-four hours, and at any time one feels inclined to do so.
The believer is entirely free to choose any one of these three prayers, but is under the obligation of reciting either one of them, and in accordance with any specific directions with which they may be accompanied.
(To a National Spiritual Assembly on behalf of Shoghi Effendi, dated 10 January 1936)