Riyad as-Salihin, Book 1, Hadith 152 (In-Book) ⓘ

Ibn 'Abbas (May Allah be pleased with them) reported: While the Prophet was delivering Khutbah (religious talk), he noticed a man who was standing, so he asked about him and was told that he was Abu Israel who had taken a vow to remain standing and not sit, or go into the shade, or speak while observing fasting. Thereupon Messenger of Allah said, "Tell him to speak, to go into the shade, to sit and to complete his fast".[Al- Bukhari].

- وعن ابن عباس رضي الله عنهما قال‏:‏ بينما النبي صلى الله عليه وسلم يخطب إذا هو برجل قائم، فسأل عنه فقالوا‏:‏ أبو إسرائيل نذر أن يقوم في الشمس ولا يقعد، ولا يستظل ولا يتكلم، ويصوم، فقال النبي صلى الله عليه وسلم‏:‏ ‏ "‏مروه فليتكلم وليستظل وليقعد وليتم صومه‏" ‏ ‏(‏‏(‏رواه البخاري‏)‏‏)‏‏.‏