Musannaf Ibn Abi Shayba 3:5976

Waki' narrated to us, from Mis'ar, from Abu Mus'ab al-Aslami, that a young boy from Aslam used to serve the Prophet (may Allah bless him and grant him peace). He served him well, so he said, "O Messenger of Allah, supplicate to Allah for me that He may admit me into Paradise or place me in your intercession." He said, "Yes, but help me [to do so] by performing many prostrations."