Hassan ibn Ahmad reported: He asked the commander of the faithful Al-Ma’mun ‘Ali ibn Musa al-Rida, may Allah have mercy on him, “Is there any benefit to fasting in the wisdom?” Al-Ma’mun said, “Allah Almighty knows what the impoverished endure of severe hunger, so He made the rich perform fasting that by necessity they might taste the flavor of hunger, until they do not forget the severe hunger of the impoverished.”
Source: Tārīkh Baghdād 18/161
Ibn Rajab reported: Some of the righteous predecessors were asked, “Why has fasting been instituted?” They said, “That the rich will taste hunger and thus will not forget the hungry.”
Source: Laṭāʼif al-Maʻārif 1/168
عن حَسَّان بْن أَحْمَد الْهَاشِمِيَّ قَالَ سَأَلَ الْمَأْمُونُ عَلِيَّ بْنَ مُوسَى الرِّضَا رحمه الله أَيُّ شَيْءٍ فَائِدَةُ الصَّوْمِ فِي الْحِكْمَةِ فَقَالَ عَلِمَ اللَّهُ مَا يَنَالُ الْفَقِيرُ مِنْ شِدَّةِ الْجُوعِ فَأَدْخَلَ عَلَى الْغَنِيِّ الصَّوْمَ لِيَذُوقَ طَعْمَ الْجُوعِ ضَرُورَةً حَتَّى لا يَنْسَى الْفَقِيرَ مِنْ شِدَّةِ الْجُوعِ
18/161 تاريخ بغداد للخطيب البغدادي
عن ابن رجب وسئل بعض السلف لم شرع الصيام قال ليذوق الغني طعم الجوع فلا ينسى الجائع
1/168 لطائف المعارف لابن رجب