Musnad Abu Ya'la al-Mawsili 149:83

'Abd al-A'la narrated to us, 'Umar ibn 'Ali narrated to us, from 'Abd al-Rahman ibn Abi Bakr, who said: I heard al-Qasim narrating from 'A'ishah that the Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever is appointed to a task and Allah intends good for him, Allah will appoint for him a sincere minister; if he forgets, he reminds him, and if he remembers, he assists him."