"The Messenger of Allah said: 'The key to prayer is purification, its opening is to say 'Allahu Akbar' and its closing is to say As-salamu 'alaikum.'"  

قَالَ رَسُولُ اللَّهِ ﷺ مِفْتَاحُ الصَّلاَةِ الطُّهُورُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ  

The Messenger of Allah said: "The key to prayer is purification, its opening is to say Allahu Akbar and its closing is to say As-salamu 'alaikum."  

عَنِ النَّبِيِّ ﷺ قَالَ مِفْتَاحُ الصَّلاَةِ الطُّهُورُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ