Thawban bin Bujdud · The Book on Vows and Oaths

"The Prophet (ﷺ) passed by old man walking (while supported) between his two sons, so he said: 'What is the matter with this one?' They said: "O Messenger of Allah! He vowed to walk.' He said: 'Verily Allah is in no need of this person punishing himself.'" He said: "So he ordered him to ride."