Musnad Ahmad 32:98

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) saw a man being supported between his two sons. He said: "What is this?" They said: "He vowed to walk [on foot for pilgrimage]." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah is in no need of this man torturing himself." So he commanded him, and he rode.