Fasting

“O Ye who believe! Fasting is prescribed to you as it was prescribed to those before you that you may become Al Muttaqoon (pious, God fearing) "(Albaqarah 183)

[Observing Saum (fasting)] for a fixed number of days, nut if any of you is ill and on a journey, the same number (should be made up) from other days. And as for those, who can fast with difficulty, (e.g. an old man), , they have (a choice either to fast or ) to feed a Miskeen(poor person) (for every day). (Al Baqarah 184)

“The month of Ramadan in which was revealed the Qur’aan, a guidance for mankind and clear proofs for the guidance and the criterion (between right and wrong). So whoever of you sights (the crescent on the first night of) the month (of Ramadan i.e. present at his home), he must fast that month, and whoever is ill or on a journey, the same number (of days which one did not observe Saum (fasting) must be made up) from other days. Allah intends for you ease and He does not want make things difficult for you. (He wants that you) must complete the same number (of days), and that you must magnify Allah (i.e. to say Takeer (Allahu Akbar; Allah is the Most Great) )” for having guided you so that you may be grateful to Him. ( Al Baqarah 185)

Definition of Fasting (saum)

In Arabic language: abstaining, refraining

In Islamic Terminology: abstinence from nullifiers from the start of fajr to sunset with intention.