Reference: Siyar A’laam an-Nubalaa
Abu Nadhrah reports that Abu Sa’eed said:
They struck him (‘Uthmaan ibn ‘Affaan) and [his] blood spilt onto the mus.haf, [specifically] on the aayah:
{And Allaah will be sufficient for you against them. And He is the Hearing, the Knowing}, soorah al-baqarah, aayah 137