From Sahih Bukhari (Hadith 1644):
Narrated Nafi`:Ibn `Umar said, "When Allah's Messenger (ﷺ) performed the first Tawaf he did Ramal in the first three rounds and then walked in the remaining four rounds (of Tawaf of the Ka`ba), where as in performing Tawaf between Safa and Marwa he used to run in the midst of the rainwater passage," I asked Nafi`, "Did `Abdullah (bin `Umar) use to walk steadily on reaching the Yemenite Corner?" He replied, "No, unless people were crowded at the Corner; otherwise he would not leave it without touching it
Reference: Bukhari 1644