Ibn Abbas reported: While the Prophet, peace and blessings be upon him, was giving a sermon, he saw a man standing and he asked about him. They said, “It is Abu Israel, who has vowed that he will stand and never sit down, he will never come into the shade, nor will he speak to anyone, and he will be fasting.” The Prophet said, “Tell him to speak, come into the shade, and sit down, but let him complete his fast.”
Source: Ṣaḥīḥ al-Bukhārī 6326
Grade: Sahih (authentic) according to Al-Bukhari
عَنْ ابْنِ عَبَّاسٍ قَالَ بَيْنَا النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَخْطُبُ إِذَا هُوَ بِرَجُلٍ قَائِمٍ فَسَأَلَ عَنْهُ فَقَالُوا أَبُو إِسْرَائِيلَ نَذَرَ أَنْ يَقُومَ وَلَا يَقْعُدَ وَلَا يَسْتَظِلَّ وَلَا يَتَكَلَّمَ وَيَصُومَ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مُرْهُ فَلْيَتَكَلَّمْ وَلْيَسْتَظِلَّ وَلْيَقْعُدْ وَلْيُتِمَّ صَوْمَهُ
6326 صحيح البخاري كتاب الأيمان والنذور باب النذر فيما لا يملك وفي معصية