Since the Qur'an, which is the direct speech of God, was revealed to the Prophet (Peace be upon him) in Arabic, it is always recited in Arabic during the Islamic prayers (salat) and at other occasions. However, renderings into all major languages are available for those who do not read Arabic. But since no one can "translate" the speech of God, these are not actually translations but are rather approximations to its meaning.
Those who know Arabic emphasize the tremendous power of the Qur'an's language and style. No rendering into another language can come anywhere close to the eloquent, earnest, moving power of the original Arabic, or do it the slightest justice. Neither can it be compared to any human speech or writings; in fact, it is well-known that the sayings (hadith) of the Prophet Peace be upon him) himself do not resemble the Qur'an in style or language.
Consequently, non-Arabic-speaking Muslims often make considerable efforts to learn to read and memorize parts of the Qur'an in Arabic.
It certainly isn't necessary to know Arabic to be a Muslim. However, when a person accepts Islam, he or she will gradually become familiar with the sound of the Qur'an and with Islamic greetings and expressions, and little by little will memorize some verses or short chapters (surahs) to use during prayers. In fact, new Muslims are often eager to learn Arabic in order to be familiar with the power and majesty of God's Book, and to be able to converse and to understand other works in Arabic.
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