Recitation must be done according to rules of pronunciation, intonation, and caesuras established by the Prophet Muhammad, though first recorded in the eight century CE. The most popular reading is that of Hafs on the authority of `asim. Qur'an reading may be based on one to three tones only. Similarly, each melodic passage centers on a single tone level, but the melodic contour and melodic passages are largely shaped by the reading rules, creating passages of different lengths whose temporal expansion is defined through caesuras. Skilled readers may read professionally for mosques in cities, although being paid for reciting the Qur'an is prohibited by Islam[citation needed].
The Qur'an is marked with twenty-six symbols, circles, rectangles, dashes and letters, some in color. These are written above, below, or beside the letters of the alphabet . They indicate the pronunciation of consonants, whether the blending of neighboring or adjacent consonants is allowed, and where recitation pauses and caesuras are forbidden and possible