Anas said that the Prophet saw an old man being supported between his sons, and on asking what was the matter with him and being told that he had taken a vow to walk,* he said, “God most high has no need that this man should punish himself,” and he ordered him to ride. In a version by Muslim on Abu Huraira’s authority he said, “Ride, old man, for God is not in need of you and your vow.”
*Mirqat, iii, 565 explains this as a vow to walk to the Ka’ba.
While the Prophet was preaching a man was standing, so he asked about him and was told that he was Abu Isra’il who had taken a vow to stand and not to sit, or go into the shade, or speak, but to fast. Thereupon the Prophet said, “Command him to speak, go into the shade, sit and complete his fast.”
Ibn ‘Abbas told that Sa'd b. ‘Ubada asked the Prophet for a decision about a vow taken by his mother who had died before fulfilling it, and that he gave decision that he should fulfil it on her behalf.