"من صلى علي في يوم الجمعة ثمانين مرة غفر الله له ذنوب ثمانين سنة..."

Abū Hurayrah reported the Prophet said:

He who send prayers upon me on Friday eighty times, Allāh will forgive eighty years of sin.

[Ibn Nu'mān graded it hasan (good)]

الصلاة عليَّ نور على الصراط ومن صلى عليَّ يوم الجمعة ثمانين مرة غفرت له ذنوب ثمانين عاماً

Abū Hurayrah also reported that the Prophet said:

Prayers upon me is a light on the Sirāt (Bridge) and the one who sends prayers upon me on Friday eighty times will be forgiven eighty years of sin.

[ Abū Nu‘aym reported it while Ibn Hajr graded it weak. Imām al-Ghazālī related it in his Ihya and al-Dāruqtnī graded it gharīb (rare).]

Note: While the classification of this hadīth is weak, it doesn’t reduce the significance of its meaning; nor does it mean that the hadīth is false, a different status altogether. However it is agreed upon that if a hadīth acted upon is graded as weak but it encourages virtuous actions, then it is commendable to act upon it in one's life. [see: Ibn Taymiyya on using lesser grades of hadith for encouraging good virtues.]