عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((مِفْتَاحُ الصَّلَاةِ الطَّهُورُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ (وَفِي لَفْظٍ) مِفْتَاحُ الصَّلَاةِ الْوُضُوءُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ))
Sayyiduna Ali (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: The key to prayer is ablution, its sanctification is saying Allahu Akbar, and its conclusion is the greeting of peace. And in another narration, the words are: The key to prayer is ablution, its sanctification is saying Allahu Akbar, and its conclusion is turning for the greeting of peace.