Muawiya bin Abu Sufyan reported,

I saw the Messenger of Allah ﷺ sucking his tongue, or he said his lip, meaning Hasan bin Ali, may Allah's blessings be upon him. Surely a tongue or two lips that the Messenger of Allah ﷺ has sucked will never be punished.

Azami 10165

Sahih

عن معاوية قال

رأيت رسول الله ﷺ يمص لسانه- أو قال: شفته، يعني الحسن بن علي صلوات الله عليه- وإنه لن يعذب لسان أو شفتان مصهما رسول الله ﷺ.

الأعظمي 10165صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Virtues of the Companions and reports about them
Chapter
Virtues of individual Companions and their reports
Section
Love of the Prophet ﷺ for Hasan bin Ali and reports about him
Numbering
Jami al-Kamil 10165 (2nd edition)
Azami 10165