Whoever vows to obey Allah, let him obey him, and whoever vows to disobey Allah, let him not disobey him

The Messenger of Allah (PBUH) saw a man being suported by two of his sons, so he asked: What is this? They said: O Messenger of Allah, he vowed to perform Hajj walking. He said: Allah has no need for this man to torture himself, so let him ride.