The Messenger of Allah ﷺ said: “The key to prayer is purification; entering it is takbeer and exiting it is tasleem.” (Using translation from Aḥmad 1006)   

قَالَ رَسُولُ اللهِ ﷺ مِفْتَاحُ الصَّلَاةِ الطُّهُورُ وَإِحْرَامُهَا التَّكْبِيرُ وَإِحْلَالُهَا التَّسْلِيمُ  

[Machine] "That the Messenger of Allah ﷺ said: 'The key to prayer is ablution, its sanctification is Takbeer, and its permission is Tasleem.' Abu Umar ad-Dareer exclusively reported this, as claimed by Ibn Saad, and many of the scholars have followed him. Habban bin Hilal also narrated it from Hassan, and it is Hassan who exclusively reported it. Abu Nasr Umar bin Abdul Aziz bin Qatadah narrated it, Abu Amr reported on the authority of Abu al-Abbas ibn Abi ad-Dummek, who reported on the authority of Abdullah al-Ayshiyy, who reported on the authority of Hassan bin Ibrahim, who reported on the authority of Abu Sufyan, who reported on the authority of Abu Nadrat, who reported on the authority of Abu Sa'id, who said: The Messenger of Allah ﷺ said: 'The key to prayer is ablution, its sanctification is Takbeer, and its permission is Tasleem.' This is the narration that Abu Sufyan Tarif as-Sa'di preserved, and the hadith of Abu Sa'id is often mentioned."  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ مِفْتَاحُ الصَّلَاةِ الْوُضُوءُ وَتَحْرِيمُهَا التَّكْبِيرُ وَتَحْلِيلُهَا التَّسْلِيمُ تَفَرَّدَ بِهِ أَبُو عُمَرَ الضَّرِيرُ هَكَذَا فِيمَا زَعَمَ ابْنُ صَاعِدٍ وَكَثِيرٌ مِنَ الْحُفَّاظِ وَقَدْ تَابَعَهُ عَلَيْهِ حَبَّانُ بْنُ هِلَالٍ عَنْ حَسَّانَ فَحَسَّانُ هُوَ الَّذِي تَفَرَّدَ بِهِ وَقَدْ 3972 أنبأ أَبُو نَصْرٍ عُمَرُ بْنُ عَبْدِ الْعَزِيزِ بْنِ قَتَادَةَ أنبأ أَبُو عَمْرٍو ثنا أَبُو الْعَبَّاسِ بْنُ أَبِي الدُّمَيْكِ ثنا عَبْدُ اللهِ الْعَيْشِيُّ ثنا حَسَّانُ بْنُ إِبْرَاهِيمَ عَنْ أَبِي سُفْيَانَ عَنْ أَبِي نَضْرَةَ عَنْ أَبِي سَعِيدٍ قَالَ قَالَ رَسُولُ اللهِ ﷺ مِفْتَاحُ الصَّلَاةِ الْوُضُوءُ وَالتَّكْبِيرُ تَحْرِيمُهَا وَالتَّسْلِيمُ تَحْلِيلُهَا هَذَا هُوَ الْمَحْفُوظُ عَنْ أَبِي سُفْيَانَ طَرِيفٍ السَّعْدِيِّ وَحَدِيثُ أَبِي سَعِيدٍ يَدُورُ عَلَيْهِ  

[Machine] He said that the Messenger of Allah ﷺ said, "Wudu is the key to prayer, and the takbeer is its sanctification, and the tasleem is its release. In every two units of prayer, there is a tasleem, and a prayer is not valid except with the opening chapter of the book (Quran) and another chapter along with it." Abu Abdur Rahman said, "So I asked Abu Hanifa, 'What does it mean by a tasleem in every two units of prayer?' He said, 'It means the tashahhud, and likewise.'"  

أَنَّهُ قَالَ قَالَ رَسُولُ اللهِ ﷺ الْوُضُوءُ مِفْتَاحُ الصَّلَاةِ وَالتَّكْبِيرُ تَحْرِيمُهَا وَالتَّسْلِيمُ تَحْلِيلُهَا وَفِي كُلِّ رَكْعَتَيْنِ تَسْلِيمٌ وَلَا تُجْزِي صَلَاةٌ إِلَّا بِفَاتِحَةِ الْكِتَابِ وَمَعَهَا غَيْرُهَا قَالَ أَبُو عَبْدِ الرَّحْمَنِ فَقُلْتُ لِأَبِي حَنِيفَةَ مَا يَعْنِي فِي كُلِّ رَكْعَتَيْنِ تَسْلِيمٌ قَالَ يَعْنِي التَّشَهُّدَ وَكَذَلِكَ  

[Machine] The Prophet of Allah ﷺ used to turn to the people with his face when he sat at the end of his prayer before reciting the Tashahhud. This was before he said the Tasleem.  

كَانَ رَسُولُ اللهِ ﷺ إِذَا قَعَدَ فِي آخِرِ صَلَاتِهِ قَبْلَ التَّشَهُّدِ أَقْبَلَ عَلَى النَّاسِ بِوَجْهِهِ وَذَلِكَ قَبْلَ أَنْ يَنْزِلَ التَّسْلِيمُ