Maliks Muwatta Book 015, Hadith Number 004.

Section : About the Division of the Qur'an into Sections (Hizbs).

Yahya related to me from Malik that Yahya ibn Said said, "Once Muhammad ibn Yahya ibn Habban and I were sitting down, and Muhammad called a man over to him and said to him, 'Tell me what you have heard from your father.' The man replied that his father had told him that he went to Zayd ibn Thabit and asked him, 'What do you think of reciting the whole Qur'an in seven days?' Zayd said, 'That's good, but I prefer to recite it in two weeks, or ten days. Ask me why that is.' He said, 'I ask you then.' Zayd said, 'So that I can reflect on it and pause in it.'"