"if your evil deeds outweighed a feather, we'd feed your soul and your heart to Ammet"

In the Egyptian Book of the Dead, a dead person's heart was weighed against the goddess Ma'at, who was represented by an ostrich feather. 

If the scales balanced, Anubis would take the dead person to Osiris. If they did not then the dead person would be given to Ammit the Devourer and they would not have an afterlife.