From Sahih Bukhari (Hadith 3541):
Narrated As-Sa'ib bin Yazid:My aunt took me to Allah's Messenger (ﷺ) and said, "O Allah's Messenger (ﷺ)! My nephew is sick."' The Prophet (ﷺ) passed his hands over my head and blessed me. Then he performed ablution and I drank the remaining water, and standing behind him, I saw the seal in between his shoulders
Reference: Bukhari 3541