Here, Omar Suleiman quotes al-Fudayl ibn 'Iyad, that the smaller one sees his sins, the greater they are in the eye of Allah, and vice versa. Can someone provide a reliable source for that quote?
The correct quote is (my own translation, but maybe yours is better)
قال: بقدر ما يصغر الذنب عندك يعظم عند الله، وبقدر ما يعظم عندك يصغر عند الله.
He said: in the same manner that a sin may appear small to you it is regarded major by Allah. And in the same way it appears big to you it is regarded small by Allah.
This is mentioned in al-Jawaab al-Kafy الجواب الكافي of ibn Qayyim al-Jawziyyah, in Siyar a'Alaam an-Nubala' سير أعلام النبلاء of imam a-Dhahabi (both without a narrator chain) and maybe among the earliest sources mentioning it with a chain you may find al-Hilyah حلية الأولياء (see here) of abu Nu'aym. An earlier source might be ibn Abi ad-Dunya's at-Tawbah التوبة (see here):