عَنْ صَدَقَةَ الدِّمَشْقِيِّ قَالَ: جَاءَ رَجُلٌ إِلَى ابْنِ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُ يَسْأَلُهُ عَنِ الصِّيَامِ، فَقَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ يَقُولُ: ((إِنَّ مِنْ أَفْضَلِ الصِّيَامِ صِيَامَ أَخِي دَاوُدَ، كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا))
Sadaqa Damashqi says that a man came to Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) and asked about fasting. He said that the Messenger of Allah (peace and blessings be upon him) said: The most virtuous fasts are those of my brother Dawood (peace be upon him); he would fast one day and leave it the next day.