I saw the Prophet ﷺ carrying Hasan bin Ali on his shoulder while his saliva was dripping onto him.
حدثنا وكيع حدثنا حماد بن سلمة عن محمد يعني ابن زياد
رأيت النبي ﷺ حاملا الحسن بن علي على عاتقه ولعابه يسيل عليه
Its isnad is sahih. Ibn Majah related it in 1/216, no. 658, in the chapter on purification, saliva touching the garment, and he said in Zawaid, "Its narrators are the narrators of the Sahih."