What is the authenticity of the saying that whoever prays Asr on Friday and says in the place where he prayed, "O Allah, bless Muhammad, the unlettered Prophet, and his family and companions, and grant them peace" 80 times, Allah will forgive his sins of eighty years, and if he dies before the eighty or prays more, the remainder will go to his parents or children? And will the doer be rewarded even if it is not authentic?

The hadith (definition) you inquired about was cited by Al-Ghazali in "Ihya' 'Ulum al-Din" with the wording: "Whoever sends blessings upon me eighty times on Friday, Allah will forgive him the sins of eighty years." And it is said in it: "O Allah, bless Muhammad, Your servant, Prophet, and unlettered Messenger." This hadith was narrated by Al-Daraqutni from the narration of Ibn al-Musayyab from Abu Hurayrah. Al-Daraqutni said about it: "A gharib (strange) hadith," while Ibn al-Nu'man said: "A hasan (definition) (good) hadith." Therefore, there is a difference of opinion regarding its authentication (taḥsīn) and weakening (taḍ'īf).