Abu Dawud Book 1, Hadith Number 61.Abu Dawud Book 1. Purification Chapter : Ablution is obligatory for prayer. Narated By Ali ibn Abu Talib : The key to prayer is purification; its beginning is takbir and its end is taslim. Related Previous Post Abu Dawud Book 1, Hadith Number 62. Next Post Abu Dawud Book 1, Hadith Number 60.