Musannaf Ibn Abi Shayba 33:430

Mu'tamir ibn Sulayman narrated to us, from al-Taymi, from Abu 'Uthman, from Salman, who said: When Allah created Adam, He said: "One is for Me, one is for you, and one is between Me and you. As for the one that is for Me, it is that you worship Me and do not associate anything with Me. As for the one that is for you, it is that whatever you do of deeds, I will reward you for it. As for the one that is between Me and you, it is that from you is the supplication, and upon Me is the response."