يَا أَيُّهَا الَّذِينَ آمَنُوا كُتِبَ عَلَيْكُمُ الصِّيَامُ كَمَا كُتِبَ عَلَى الَّذِينَ مِنْ قَبْلِكُمْ لَعَلَّكُمْ تَتَّقُونَ [2–183] 

O you who believe! fasting is prescribed for you, as it was prescribed for those before you, so that you may guard (against evil). 

Fasting or Ṣawm (Arabic: صوم) ranks amongst the most significant obligatory rituals in Islam. Muslims must abstain from several activities, including eating and drinking from dawn to dusk, to obey God's command. Fasting is one of the ten Ancillaries of the Faith, and it has also been obligatory in other religions in a different manner.