Muwatta Malik #260

Yahya related to me from Malik from Zayd ibn Aslam from his father that Umar ibn al-Khattab used to pray as much as Allah willed in the night until at the end of the night he would wake his family for the prayer. He used to say to them, "The prayer, the prayer." Then he would recite the ayat, "Enjoin prayer on your family and be constant in it. We do not ask you for your provision. We provide for you. And the end result is for taqwa." (Sura 20 ayat 132)