Hadith 8:2462
Abu Bakr narrated to us, he said: Waki’ narrated to us, from Hilal ibn Abi Maymunah, he said: I saw Anas performing Tawaf. When he reached the Corner (al-Hajar), he would say "Allahu Akbar" (God is the Greatest), and he would begin and end with it.
حدثنا أبو بكر قال حدثنا وكيع عن هلال بن أبي ميمونة قال رأيت أنسا يطوف فإذا انتهى إلى الحجر كبر ويفتتح ويختم به