Saa-ib bin Yazid RA said:
"My (maternal) aunt took to me to the Holy Prophet SAW and said to him, "this nephew of mine is ill". Rasulullah (SAW) wiped his holy hand over my head and made du'a for barakah for me."
According to the evidence explained by some Ulama, Rasulullah SAW wiped his hand over his head, meant that he, Saa-ib bin Yazid RA had a pain in the head. Others opine that this is taken to mean that the Holy Prophet SAW wiped his hands in kindness on the head of Saa-ib bin Yazid RA.
Saa-ib bin Yazid RA was born in the second year Hijri, and at the time of the Holy Prophet SAW's death, his age was not more than eight or nine years. That is why the Holy Prophet SAW wiped his Holy hand in kindness, as is the customs of great personalities.
The Holy Prophet SAW also gave him the water of wudhu to drink as a cure, as will be stated further, or he may have prescibed another remedy, especially when we learn also in a narration in Sahih Bukhari thay he - Saa-ib bin Yazid RA was suffering from pain in his leg:
"When the Holy Prophet (SAW) performed wudhu, I drank the water of that wudhu."
As a brief explanation to the above, the Holy Prophet SAW may have performed wudhu for some reason, but here it is clear that the Holy Prophet SAW performed wudhu so that the water could be used as a remedy and medicine.
The narrator further continues:
"I saw the seal of Prophethood, which was like the knot on a mosquito net or bedstead." (Which is the size of a pigeon's egg in roundness).