View source for Intercalation and Commutation prohibited by the Qur’an, 631 CE

If the Prophet adopted the 19 year lunar-solar cycle, it was soon canceled.  Al-Tabari in his ''Ta'rikh al-Rusul wa'l Muluk'' gives the following exposition: 

:The Prophet on the occasion of the Hajjat al Wada' said:  O people! Time after undergoing a full revolution has returned to its original state; the day Allah created the heavens and the earth. (vol. iii, p.l50, Cairo 1969).<ref>The Lift of Mahomet, William Muir, Esq., Smith, Elder, & Co., London, 1861, Chapter III, Section 4.</ref>

The Qur’an Chapter 9, refers to twelve (12) months, and prohibits the manipulation of the Calendar.  Sura at-Taubah 9: 36 and 37, specifically deals with the manipulation of the Calendar by the Jewish system by intercalation:

:Surely the number of months with Allah is twelve months in Allah's ordinance since the day when He created the heavens and the earth, of these four being sacred; that is the right reckoning; therefore be not unjust to yourselves regarding them, and fight the polytheists all together as they fight you all together; and know that Allah is with those who guard (against evil). (9:36)

:Postponing (of the sacred month) is only an addition in unbelief, wherewith those who disbelieve are led astray, violating it one year and keeping it sacred another, that they may agree in the number (of months) that Allah has made sacred, and thus violate what Allah has made sacred; the evil of their doings is made fair-seeming to them; and Allah does not guide the unbelieving people. (9:37)

:He it is who appointed the sun a splendor and the moon a light and measured for her stages, that ye might know the number of the years, and the reckoning. (10:5) 

The purport of these Qur'anic verses is that we must take the moon to be the source of the calendar, and any other system that would be unnatural will not succeed, being non-natural and, therefore, it is that the Islamic calendar is based on the strictly lunar system. Its beginnings can be traced to the Prophet, but, as a regular feature, it came into its own during the time of the second Caliph 'Umar I.

==References==
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[[Category:Islam and Judaism]]
[[Category:The Islamic Jewish Calendar]]