Sahih al-Bukhari, Volume 3, Book 29, Hadith 82 (USC-MSA) ⓘ
Narrated As-Sa'ib bin Yazid: (While in the company of my parents) I was made to perform Hajj with Allah's Messenger and I was a seven-year-old boy then. (Fath-ul-Bari, p.443, Vol.4)
حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ يُونُسَ، حَدَّثَنَا حَاتِمُ بْنُ إِسْمَاعِيلَ، عَنْ مُحَمَّدِ بْنِ يُوسُفَ، عَنِ السَّائِبِ بْنِ يَزِيدَ، قَالَ حُجَّ بِي مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم وَأَنَا ابْنُ سَبْعِ سِنِينَ.
also referenced under: Book 28, Hadith 38 (In-Book) & Hadith 1858 (DarusSalam)