The Messenger of Allah ﷺ said: “The key to prayer is wudoo’, entering it is takbeer and exiting it is tasleem.ʿ (Using translation from Aḥmad 1072)
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «مِفْتَاحُ الصَّلَاةِ الْوُضُوءُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ»