Yes, Allah (The One God), commands Muslims through his Word (The Quran) by saying:
"Ramadan is the month during which the Quran was revealed, providing guidance for the people, clear teachings, and the statute book. Those of you who witness this month shall fast therein. Those who are ill or traveling may substitute the same number of other days. God wishes for you convenience, not hardship, that you may fulfill your obligations, and to glorify God for guiding you, and to express your appreciation. (2:185)"