КОРАН (английский перевод) - 2.185

The month of Ramadan is the month in which the Koran was sent down, a guidance for people, and clear verses of guidance and the criterion. Therefore, whoever of you witnesses the month, let him fast. But he who is ill, or on a journey shall (fast) a similar number (of days) later on. Allah wants ease for you and does not want hardship for you. And that you fulfill the number of days and exalt Allah who has guided you in order that you be thankful.