حَدَّثَنَا أَبُو مُوسَى، مُحَمَّدُ بْنُ الْمُثَنَّى حَدَّثَنَا خَالِدُ بْنُ الْحَارِثِ، حَدَّثَنَا حُمَيْدٌ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، قَالَ مَرَّ النَّبِيُّ صلى الله عليه وسلم بِشَيْخٍ كَبِيرٍ يَتَهَادَى بَيْنَ ابْنَيْهِ فَقَالَ ‏"‏ مَا بَالُ هَذَا ‏"‏ ‏.‏ قَالُوا يَا رَسُولَ اللَّهِ نَذَرَ أَنْ يَمْشِيَ ‏.‏ قَالَ ‏"‏ إِنَّ اللَّهَ عَزَّ وَجَلَّ لَغَنِيٌّ عَنْ تَعْذِيبِ هَذَا نَفْسَهُ ‏"‏ ‏.‏ قَالَ فَأَمَرَهُ أَنْ يَرْكَبَ ‏.‏

Narrated Anas: "The Prophet (PBUH) 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 [the Mighty and Sublime] is in no need of this person punishing himself.'" He said: "So he ordered him to ride." Translation Not Available

Book Ref: Jamiya Tirmidhi Book 20 Hadith 1537
Web Ref:  Jamiya Tirmidhi Vol 3 Book 18 Hadith 1537