O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous

Quran: Surah Baqarah Ayah 183

“Fasting is a shield, so when one of you is fasting, he should neither indulge in obscene language nor should he raise his voice in anger. If someone attacks him or insults him, let him say: I am fasting."

Muslim

“The five (daily) prayers, and from one Friday prayer to the next and from Ramadan to Ramadan, are expiation for sins committed in between, provided one stays away from the major sins”.

Al-Bukhari