Musnad Ahmad 1153:1780

Waki’ narrated to us, from ‘Ali ibn Salih, from Ibrahim ibn Muhajir, from Ibrahim, from ‘Aisha, who said: My necklace was stolen, so I invoked [a curse] against the one who took it. The Prophet, peace and blessings of Allah be upon him, said: "Do not lighten [the burden of] his sin; leave him to his sin."