What is the authenticity of Aisha's narration concerning the Prophet's sucking the blood of Usama from his face, and does it indicate the purity of blood discharged from the body?

The hadith is weak in its chain of transmission because it comes through the route of Shareek, who had a poor memory. However, the origin of thehadith is established by the follow-up narration of Mujalid ibn Saeed and the mursal narration of Abu Al-Safar. As for the story of the Prophet, peace and blessings be upon him, sucking blood, it is not established. And deriving evidence from this hadith for the purity of flowing blood from a wound is incorrect, due to the lack of established evidence for that addition. Flowing blood is impure by scholarly consensus, and what is pardoned is only a small amount of blood.