Fasting is primarily an institution for spiritual discipline and self-control. It has been ordained as a religious duty for the Muslims to subdue their desires and to keep their appetites well within reasonable bounds so that man may not become their slave and lose control over himself. It teaches patience and perseverance and enhances the feeling of moral accomplishment. In fact, this purpose cannot be achieved if Muslims observe fasting during night time when they are mostly sleeping.
Acts like fasting, its timing, and other rituals that are related to the category of `ibadat (acts of worship), are orders of Allah the Almighty.
We believe they have infinite wisdom, for Almighty Allah is al-Hakeem (the All-Wise). He does not order anything unwise, and yet in order for us not to disrespect Allah the Almighty the scholars have classified them as ta`abbudi acts, which means that we cannot pinpoint one particular reason in the sense that if that reason is not there we can dispense with the act. The ta`abbudi acts are rituals that we must fulfil regardless of whether their immediate benefits are clear to us or not.
Having said this, we’d like to state that there is wisdom in fasting during daytime and not at night. Elaborating on this Dr. Muzammil H. Siddiqi, former President of the Islamic Society of North America, states:
Most people fast during the night time. When people are sleeping they do not eat. That is why the first meal of the morning is called ‘breakfast’. Fasting during the night does not need much effort or discipline. The real benefit of fast comes when one controls one’s self during the daytime.