Reference: al-Bid’u wal-Muhdathaat wa maa laa Asla lahu – Page 304
Fataawa at-Ta’ziyyah – Page 43
Question: What is the ruling regarding kissing the relatives of the deceased when conveying condolences?
Response: I do not know of kissing the relatives of the deceased when conveying condolences to be from the Sunnah. Because of this, it is not befitting for the people to adopt this as a Sunnah as anything which has not been mentioned on the authority of the Prophet ﷺ and nor his companions, it is befitting to avoid it.