Sunan Abi Dawud, Hadith 3300

Narrated Ibn 'Abbas: While the Prophet was preaching a man was standing in the sun. He asked about him. They said: He is Abu Isra'il who has taken a vow to stand and not to sit, or go into shade, or speak, but to fast. Thereupon he said: Command him to speak, to go into the shade, sit and complete his fast.

حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا وُهَيْبٌ، حَدَّثَنَا أَيُّوبُ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ ‏:‏ بَيْنَمَا النَّبِيُّ صلى الله عليه وسلم يَخْطُبُ إِذَا هُوَ بِرَجُلٍ قَائِمٍ فِي الشَّمْسِ فَسَأَلَ عَنْهُ قَالُوا ‏:‏ هَذَا أَبُو إِسْرَائِيلَ نَذَرَ أَنْ يَقُومَ وَلاَ يَقْعُدَ، وَلاَ يَسْتَظِلَّ وَلاَ يَتَكَلَّمَ وَيَصُومَ ‏.‏ قَالَ ‏:‏ ‏ "‏ مُرُوهُ فَلْيَتَكَلَّمْ وَلْيَسْتَظِلَّ وَلْيَقْعُدْ، وَلْيُتِمَّ صَوْمَهُ ‏" ‏ ‏.‏

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also referenced under: Hadith 3294 (Hasan)