Musnad Ahmad 1045:1

Muhammad ibn Fudayl narrated to us, from ‘Ata’, from Abu ‘Abd al-Rahman, who said: Those who used to teach us from the companions of the Prophet (may Allah bless him and grant him peace) narrated to us that they used to learn ten verses from the Messenger of Allah (may Allah bless him and grant him peace). They would not proceed to the next ten until they had learned what was in these [ten] regarding knowledge and action. They said: So we learned knowledge and action.