[Machine] The prayer is ordained as two units, except for Maghrib prayer which is ordained as three units, because it is the Witr prayer. The Messenger of Allah ﷺ used to pray the initial prayer (when traveling) as two units, except for Maghrib prayer, and when he stayed, he would add two units to each unit except for Maghrib prayer, because it is the Witr prayer, and Fajr prayer because he would prolong the recitation in it.  

فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ رَكْعَتَيْنِ إِلَّا الْمَغْرِبَ فُرِضَتْ ثَلَاثًا لِأَنَّهَا وِتْرٌ قَالَتْ وَكَانَ رَسُولُ اللهِ ﷺ إِذَا سَافَرَ صَلَّى الصَّلَاةَ الْأُولَى إِلَّا الْمَغْرِبَ فَإِذَا أَقَامَ زَادَ مَعَ كُلِّ رَكْعَتَيْنِ رَكْعَتَيْنِ إِلَّا الْمَغْرِبَ لِأَنَّهَا وَتْرٌ وَالصُّبْحَ لِأَنَّهُ يُطَوِّلُ فِيهَا الْقِرَاءَةَ  

[Machine] "The prayers for traveling and residing were prescribed as two units. However, when the Messenger of Allah ﷺ established the prayer, he prayed four units. The Fajr prayer was left behind due to the lengthy recitation, and the Maghrib prayer was left behind because it is the odd prayer of the day."  

«فُرِضَتْ صَلَاةُ السَّفَرِ وَالْحَضَرِ رَكْعَتَيْنِ فَلَمَّا أَقَامَ رَسُولُ اللَّهِ ﷺ رَكْعَتَانِ رَكْعَتَانِ وَتُرِكَتْ صَلَاةُ الْفَجْرِ لِطُولِ الْقِرَاءَةِ وَصَلَاةُ الْمَغْرِبِ لِأَنَّهَا وِتْرُ النَّهَارِ»  

[Machine] The first prayer that was made obligatory was two units (rak'ahs). When the Prophet ﷺ arrived in Madinah and settled down, he added two more units of prayer, excluding the Maghrib prayer, because it is odd in number. As for the Fajr prayer, he added more units due to its lengthy recitation. It is said that when he traveled, he would perform his first prayer.  

إِنَّ أَوَّلَ مَا فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ فَلَمَّا قَدِمَ نَبِيُّ اللهِ ﷺ الْمَدِينَةَ وَاطْمَأَنَّ زَادَ رَكْعَتَيْنِ غَيْرَ الْمَغْرِبِ لِأَنَّهَا وِتْرٌ وَصَلَاةُ الْغَدَاةِ لِطُولِ قِرَاءَتِهَا قَالَتْ وَكَانَ إِذَا سَافَرَ صَلَّى صَلَاتَهُ الْأُولَى