Once a person asked Messenger of Allah ﷺ ﷺ about the night prayer. Allah's Apostle ﷺ replied, "The night prayer is offered as two Rakʿat followed by two Rakʿat and so on and if anyone is afraid of the approaching dawn (Fajr prayer) he should pray one Rakʿah and this will be a Witr for all the Rakʿat which he has prayed before."  

أَنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ ﷺ عَنْ صَلاَةِ اللَّيْلِ فَقَالَ رَسُولُ اللَّهِ ﷺ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خَشِيَ أَحَدُكُمُ الصُّبْحَ صَلَّى رَكْعَةً وَاحِدَةً تُوتِرُ لَهُ مَا قَدْ صَلَّى  

Nafiʿ told that ʿAbdullah bin ʿUmar used to say Taslim between (the first) two Rakʿat and (the third) odd one in the Witr prayer, when he wanted to attend to a certain matter (during that interval between the Rakʿat).  

أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ يُسَلِّمُ بَيْنَ الرَّكْعَةِ وَالرَّكْعَتَيْنِ فِي الْوِتْرِ حَتَّى يَأْمُرَ بِبَعْضِ حَاجَتِهِ  

Once I passed the night in the house of Maimuna (his aunt). I slept across the bed while Allah's Apostle and his wife slept length-wise. The Prophet ﷺ slept till midnight or nearly so and woke up rubbing his face and recited ten verses from Surat "Al-ʿImran." Messenger of Allah ﷺ went towards a leather skin and performed ablution in the most perfect way and then stood for the prayer. I did the same and stood beside him. The Prophet ﷺ put his right hand on my head, twisted my ear and then prayed two rakʿat five times and then ended his prayer with witr. He laid down till the Mu'adh-dhin came then he stood up and offered two rakʿat (Sunnah of Fajr prayer) and then went out and offered the Fajr prayer. (See Hadith 183)  

أَخْبَرَهُ أَنَّهُ بَاتَ عِنْدَ مَيْمُونَةَ وَهْىَ خَالَتُهُ فَاضْطَجَعْتُ فِي عَرْضِ وِسَادَةٍ وَاضْطَجَعَ رَسُولُ اللَّهِ ﷺ وَأَهْلُهُ فِي طُولِهَا فَنَامَ حَتَّى انْتَصَفَ اللَّيْلُ أَوْ قَرِيبًا مِنْهُ فَاسْتَيْقَظَ يَمْسَحُ النَّوْمَ عَنْ وَجْهِهِ ثُمَّ قَرَأَ عَشْرَ آيَاتٍ مِنْ آلِ عِمْرَانَ ثُمَّ قَامَ رَسُولُ اللَّهِ ﷺ إِلَى شَنٍّ مُعَلَّقَةٍ فَتَوَضَّأَ فَأَحْسَنَ الْوُضُوءَ ثُمَّ قَامَ يُصَلِّي فَصَنَعْتُ مِثْلَهُ فَقُمْتُ إِلَى جَنْبِهِ فَوَضَعَ يَدَهُ الْيُمْنَى عَلَى رَأْسِي وَأَخَذَ بِأُذُنِي يَفْتِلُهَا ثُمَّ صَلَّى رَكْعَتَيْنِ ثُمَّ رَكْعَتَيْنِ ثُمَّ رَكْعَتَيْنِ ثُمَّ رَكْعَتَيْنِ ثُمَّ رَكْعَتَيْنِ ثُمَّ رَكْعَتَيْنِ ثُمَّ أَوْتَرَ ثُمَّ اضْطَجَعَ حَتَّى جَاءَهُ الْمُؤَذِّنُ فَقَامَ فَصَلَّى رَكْعَتَيْنِ ثُمَّ خَرَجَ فَصَلَّى الصُّبْحَ  

The Prophet ﷺ said, "Night prayer is offered as two rakʿat followed by two rakʿat and so on, and if you want to finish it, pray only one rakʿa which will be witr for all the previous rakʿat." Al-Qasim said, "Since we attained the age of puberty we have seen some people offering a three-rakʿat prayer as witr and all that is permissible. I hope there will be no harm in it."  

قَالَ النَّبِيُّ ﷺ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا أَرَدْتَ أَنْ تَنْصَرِفَ فَارْكَعْ رَكْعَةً تُوتِرُ لَكَ مَا صَلَّيْتَ قَالَ الْقَاسِمُ وَرَأَيْنَا أُنَاسًا مُنْذُ أَدْرَكْنَا يُوتِرُونَ بِثَلاَثٍ وَإِنَّ كُلاًّ لَوَاسِعٌ أَرْجُو أَنْ لاَ يَكُونَ بِشَىْءٍ مِنْهُ بَأْسٌ  

Messenger of Allah ﷺ used to pray eleven rakʿat at night and that was his night prayer and each of his prostrations lasted for a period enough for one of you to recite fifty verses before Messenger of Allah ﷺ raised his head. He also used to pray two rakʿat (Sunnah) before the (compulsory) Fajr prayer and then lie down on his right side till the Mu'adh-dhin came to him for the prayer.  

أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُصَلِّي إِحْدَى عَشْرَةَ رَكْعَةً كَانَتْ تِلْكَ صَلاَتَهُ تَعْنِي بِاللَّيْلِ فَيَسْجُدُ السَّجْدَةَ مِنْ ذَلِكَ قَدْرَ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً قَبْلَ أَنْ يَرْفَعَ رَأْسَهُ وَيَرْكَعُ رَكْعَتَيْنِ قَبْلَ صَلاَةِ الْفَجْرِ ثُمَّ يَضْطَجِعُ عَلَى شِقِّهِ الأَيْمَنِ حَتَّى يَأْتِيَهُ الْمُؤَذِّنُ لِلصَّلاَةِ