It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that a man called Abu Isra'il vowed that he would not speak, would not seek shade, would not sit, and would fast that day. The Messenger of Allah (peace and blessings be upon him) said: "Order him to speak, to seek shade, to sit, and to complete his fast."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11821