There is a sermon in Nahjul Balagha, in which the Commander of the Faithful has stated a few symbols of the obligations of the Religion of the Prophet (S.A.) Among them is this reason of
the obligation of fasting:
"Fasting was enjoined so that the sincerity of the righteous may come to light."
It is known that the righteous believes:
(i) Allah is our Creator and Lord.
(ii) He is Just and Wise.
(iii) He governs both our body and soul.
(iv) Any worship prescribed by Him for the two (body and soul) will be justified.
It is evident that if there were no physical worship the four aforesaid articles of Faith would remain concealed and the righteous and the evil doer would not be differentiated. Allah has
provided an opportunity for the manifestation of these beliefs by enjoining the bodily worship. Therefore those who observe fast and offer prayers thereby demonstrate their beliefs which are
inner states and invisible.
Fasting thoroughly tries the righteous and shows that the observer of fast is humble. It reminds him of the hunger and thirst of the destitute and he deals with them according to the
Religion of Mohammad (S.A.)
If his soul is more purified, his vision reaches upto Day of Resurrection and is imbued with the idea of hunger and thirst on that day Fasting, therefore, is all the more sweet to him
because the 'Sharey' (exponent of the religion) has said that to be hungry and thirsty here, by the Order of Allah will save a person from the hunger and thirst on the Day of Judgment.