Hadith: O Messenger of Allah, my nephew is ailing. So he wiped over my head and invoked blessings upon me. Then he performed ablution and I drank from the water of his ablution. After that, I stood behind his back and looked at the seal of prophet-hood between his two shoulder blades, and it resembled the egg of a pigeon

عن الجعْد، قال: سمعتُ السَّائِب بن يَزيد، يقول: ذهبتْ بي خالتي إلى النبي صلى الله عليه وسلم فقالت: يا رسول الله، إنَّ ابنَ أختي وَجِعٌ. فمَسَح رأسي ودعا لي بالبَرَكة، ثم توضَّأ، فشربتُ من وَضوئه، ثم قمتُ خَلْف ظهره، فنَظَرتُ إلى خاتَم النبوة بيْن كتِفَيْه، مثل زِرِّ الحَجَلَة.
[صحيح] - [متفق عليه]

Al-Ja‘d reported that he heard As-Sā’ib ibn Yazīd say: "My maternal aunt took me to the Prophet (may Allah's peace and blessings be upon him) and said: 'O Messenger of Allah, my nephew is ailing.' So he wiped over my head and invoked blessings upon me. Then he performed ablution and I drank from the water of his ablution. After that, I stood behind his back and looked at the seal of prophet-hood between his two shoulder blades, and it resembled the egg of a pigeon."
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

In this Hadīth, As-Sā’ib ibn Yazīd explains that his maternal aunt took him to the Prophet (may Allah's peace and blessings be upon him) and told him that he was ailing. So the Prophet (may Allah's peace and blessings be upon him) wiped over his head and invoked blessings upon him. Then he performed ablution, and As-Sā’ib drank from the water dripping from his blessed organs during ablution. Later, As-Sā’ib stood behind the back of the Prophet (may Allah's peace and blessings be upon him) and looked at the seal of prophet-hood between his two shoulder blades, which resembled a pigeon's egg.