Musnad Ahmad 25:810

Yunus narrated to us, Layth narrated to us, from Qays ibn al-Hajjaj, from Hanash al-San'ani, from Abdullah ibn Abbas, that he narrated to him: That he rode behind the Messenger of Allah (peace and blessings of Allah be upon him) one day, and the Messenger of Allah (peace and blessings of Allah be upon him) said to him: "O young boy, I am teaching you some words: Guard Allah, and He will guard you. Guard Allah, and you will find Him before you. If you ask, ask Allah; and if you seek help, seek help from Allah. And know that if the nation were to gather together to benefit you, they would not benefit you except with something that Allah has already written for you. And if they were to gather together to harm you, they would not harm you except with something that Allah has already written against you. The pens have been lifted, and the scrolls have dried."