Musannaf Ibn Abi Shayba 21:199

Abu al-Ahwas narrated to us, from Mansur, from Rib'i, from Abdullah ibn Shaddad, from Abdullah ibn Ja'far, who said: The Messenger of Allah (may Allah bless him and grant him peace) said to me: "Shall I not teach you words that I have not taught to Hasan nor Husayn? If you seek a need and desire for it to be successful, then say: 'There is no god but Allah alone, He has no partner, the Most High, the Almighty. And there is no god but Allah alone, He has no partner, the Wise, the Generous.' Then ask for your need."