The early Muslim community did not really have a symbol. During the time of the Prophet Muhammad (peace and blessings be upon him) countries and caravans flew simple solid-coloured flags (generally black, green, or white) for identification purposes. In later generations, the Muslim leaders continued to use a simple black, white, or green flag with no markings, writing, or symbolism on it.
It wasn’t until the Ottoman Empire that the crescent moon and star became affiliated with the Muslim world. When the Turks conquered Constantinople (Istanbul) in 1453, they adopted the city’s existing flag and symbol.
The symbol of Islam IS NOT the crescent moon and the star, but it was used by the last Islamic Dynasty, the Ottoman’s. The Ottoman Empire deemed it appropriate to use the star and crescent as their symbols, but not the symbols of Islam.
In conclusion, the star and the crescent moon are not a part of the religion of Islam.