From Sahih Bukhari (Hadith 1606):
Narrated Nafi`:Ibn `Umar. said, "I have never missed the touching of these two stones of Ka`ba (the Black Stone and the Yemenite Corner) both in the presence and the absence of crowds, since I saw the Prophet (ﷺ) touching them." I asked Nafi`: "Did Ibn `Umar use to walk between the two Corners?" Nafi` replied, "He used to walk in order that it might be easy for him to touch it (the Corner Stone)
Reference: Bukhari 1606