The virtue of fasting, and the different reports from Abu Ishaq in the Hadith of 'Ali bin Abi Talib about that
أَخْبَرَنِي هِلاَلُ بْنُ الْعَلاَءِ، قَالَ حَدَّثَنَا أَبِي قَالَ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ زَيْدٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَبْدِ اللَّهِ بْنِ الْحَارِثِ، عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " إِنَّ اللَّهَ تَبَارَكَ وَتَعَالَى يَقُولُ الصَّوْمُ لِي وَأَنَا أَجْزِي بِهِ وَلِلصَّائِمِ فَرْحَتَانِ حِينَ يُفْطِرُ وَحِينَ يَلْقَى رَبَّهُ وَالَّذِي نَفْسِي بِيَدِهِ لَخُلُوفُ فَمِ الصَّائِمِ أَطْيَبُ عِنْدَ اللَّهِ مِنْ رِيحِ الْمِسْكِ " .
It was narrated from 'Ali bin Abi Talib that the Messenger of Allah (ﷺ) said: "Allah, may He be blessed and exalted, says: 'Fasting is for me and I shall reward for it. The fasting person has two moments of joy: When he breaks his fast and when he meets his Lord.' By the One in whose hand is my soul, the smell that comes from the mouth of the fasting person is better before Allah than the fragrance of musk." '