“The most important of your affairs, to me, is the prayer. Whoever guards it and keeps to it has guarded his religion, and whoever neglects it will neglect everything else even more.”

‘Umar ibn al-Khattab wrote this to his governors, and Malik records the letter at the start of the book on prayer times in the Muwatta’: it goes straight on to set out when each prayer should be prayed. That a caliph’s letter to the men governing his provinces was about the prayer — first its importance, then its exact times — is itself the lesson.