While the Prophet (ﷺ) 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.
Reference: Sunan Abi Dawud 3300 In-book : Book 22, Hadith 59 English translation : Book 21, Hadith 3294
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