Al-Qur'an:

"The month of Ramadan (is the month) in which the Qur'an has been sent down as guidance for mankind containing clear signs which lead (to the straight road) and distinguishing (the truth from falsehood).." (Q 2:185)

Oh you who believe! Fasting is prescribed to you as it was prescribed to those before you, that you many learn piety and righteousness" (Q 2:183)

Fasting is prescribed for you as it was prescribed for those before you, that you may attain taqwaa." (Q2:183)

The most honored by Allah amongst you are those best in taqwaa."(Q 49:13)

..And it is better for you that ye fast, if ye only knew." (Q 2:184)

"Indeed We have revealed it (Qur'an) in the night of Power. And what will explain to you what the night of Power is? The night of Power is better than a thousand months. Therein descends the Angels and the Spirit (Jibreel) by Allah's permission, on every errand: (they say) "Peace" (continuously) till the rise of Morning!" (Q 97:1-5)

We sent it (this Qur'an) down on a blessed Night. Verily, We are ever warning (mankind of Our Torment). Therein (that Night) is decreed every matter of ordainment. Amran (i.e. a command or this Qur'an or His Decree of every matter) from Us. Verily, We are ever sending (the Messenger). (As) a Mercy from your Lord. Verily! He is the All-Hearer, the All-Knower." (Ad-Dukhaan 44: 3-6)