A man asked the Messenger of Allah ﷺ about the prayer at night. The Messenger of Allah ﷺ said: Prayer during the night should consist of pairs of rak'ahs, but if one of you fears the morning is near he should pray one rak'ah which will make his prayer an odd number for him. (Using translation from Abū Dāʾūd 1326)   

أَنَّ رَجُلًا سَأَلَ رَسُولَ اللهِ ﷺ عَنْ صَلَاةِ اللَّيْلِ فَقَالَ رَسُولُ اللهِ ﷺ صَلَاةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا خَشِيَ أَحَدُكُمُ الصُّبْحَ صَلَّى رَكْعَةً تُوتِرُ لَهُ مَا قَدْ صَلَّى  

[Machine] The Messenger of Allah ﷺ said, "The night prayer should be performed in sets of two. When you see that dawn is approaching, then conclude with one unit of prayer." A man asked Ibn Umar, "What does 'sets of two' mean?" He replied, "You make Salaam after every two units of prayer."  

قَالَ رَسُولُ اللهِ ﷺ صَلَاةُ اللَّيْلِ مَثْنَى مَثْنَى فَإِذَا رَأَيْتَ أَنَّ الصُّبْحَ مُدْرِكُكَ فَأَوْتِرْ بِرَكْعَةٍ فَقَالَ رَجُلٌ لِابْنِ عُمَرَ مَا مَثْنَى؟ قَالَ تُسَلِّمُ فِي كُلِّ رَكْعَتَيْنِ  

[Machine] Aisha, the wife of the Prophet ﷺ , said: The Prophet ﷺ used to pray eleven Rak'ahs (units of prayer) between the end of the night prayer (Isha) and the dawn prayer (Fajr). He would offer the Salaam (concluding the prayer) after every two Rak'ahs, and he would perform the Witr prayer (an odd-numbered prayer) with one Rak'ah. He would also make a long prostration, equivalent to reciting fifty verses of the Qur'an, before raising his head (from prostration). When the caller to prayer finishes the Fajr prayer and the dawn becomes clear to him, the Prophet ﷺ would get up and pray two light Rak'ahs, and then he would lie down on his right side until the caller to prayer comes to give the call for the Iqamah (the final announcement before prayer). He would then come out with the caller to prayer. Some of them add a little to this.  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ كَانَ النَّبِيُّ ﷺ يُصَلِّي فِيمَا بَيْنَ أَنْ يَفْرُغَ مِنْ صَلَاةِ الْعِشَاءِ إِلَى الْفَجْرِ إِحْدَى عَشْرَةَ رَكْعَةً يُسَلِّمُ مِنْ كُلِّ رَكْعَتَيْنِ وَيُوتِرُ بِوَاحِدَةٍ وَيَسْجُدُ سَجْدَةً قَدْرَ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً قَبْلَ أَنْ يَرْفَعَ رَأْسَهُ فَإِذَا سَكَتَ الْمُؤَذِّنُ مِنْ صَلَاةِ الْفَجْرِ وَتَبَيَّنَ لَهُ الْفَجْرُ قَامَ فَرَكَعَ رَكْعَتَيْنِ خَفِيفَتَيْنِ ثُمَّ اضْطَجَعَ عَلَى شِقِّهِ الْأَيْمَنِ حَتَّى يَأْتِيَهُ الْمُؤَذِّنُ لِلْإِقَامَةِ فَيَخْرُجَ مَعَهُ قَالَ وَبَعْضُهُمْ يَزِيدُ عَلَى بَعْضٍ