It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When two Muslims meet, shake hands and ask after each other, Allah Almighty sends down one hundred mercies between them, ninety-nine of which are for whichever of the two is more cheerful, more open-hearted, kinder, and better in asking after his brother."
Imam al-Tabarani (may Allah have mercy on him) said: "Only his son Abdullah narrated this hadith from Yahya bin Abi Kathir, and only Yahya bin Misma' narrated it from Abdullah, and al-Hasan bin Kathir is alone in it."
This is how it is in the Dar al-Haramayn edition, and the correct name is probably "Yahya bin Kathir".
Hadith Referenceالمعجم الأوسط / باب الميم / 7672
Hadith Gradingمحدثین:إسناده ضعيف لجهالة الحسن بن كثير بن عدي
Hadith Takhrij«قال الهيثمي: فيه الحسن بن كثير بن عدي ولم أعرفه وبقية رجاله رجال الصحيح «مجمع الزوائد ومنبع الفوائد، ج 8، ص 37»»