What is the ruling regarding the saliva of children?

Primary text

The saliva of children is pure. Evidence for this is the narration by Abu Hurayrah, who stated that he saw the Messenger of Allah, peace be upon him, carrying Al-Husayn upon his shoulder, and his saliva was flowing onto him. Abu Bakr also carried Al-Hasan ibn Ali upon his shoulder with his saliva flowing, while Ali was beside him, and Abu Bakr was saying, 'Oh my father, he resembles the Prophet, he does not resemble Ali,' and Ali was laughing.