Allah ﷻ prescribed the prayer, when He prescribed it, as two rakahs each, both while resident and while traveling. The prayer while traveling was left as it was, and the prayer while resident was increased.

فَرَضَ اللَّهُ الصَّلاَةَ حِينَ فَرَضَهَا رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ، فَأُقِرَّتْ صَلاَةُ السَّفَرِ، وَزِيدَ فِي صَلاَةِ الْحَضَرِ.

"When the prayers were first enjoined they were of two rakʿat each. Later the prayer in a journey was kept as it was but the prayers for non-travelers were completed." Az-Zuhri said, "I asked ʿUrwa what made Aisha pray the full prayers (in journey)." He replied, "She did the same as ʿUthman did."

قَالَتِ الصَّلاَةُ أَوَّلُ مَا فُرِضَتْ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَأُتِمَّتْ صَلاَةُ الْحَضَرِ قَالَ الزُّهْرِيُّ فَقُلْتُ لِعُرْوَةَ مَا بَالُ عَائِشَةَ تُتِمُّ قَالَ تَأَوَّلَتْ مَا تَأَوَّلَ عُثْمَانُ

The prayer was prescribed as two rak'ahs, two rak'ahs both in journey and at the place of residence. The prayer while travelling remained as it was (originally prescribed), but an addition was made in the prayer (observed) at the place of residence.

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ

'A'isha, the wife of the Messenger of Allah ﷺ, said Allah prescribed the prayer as two rak'ahs, then it was completed (to four rak'ahs) at the place of residence, but was retained in the same position in journey as it was first made obligatory.

أَنَّ عَائِشَةَ زَوْجَ النَّبِيِّ ﷺ قَالَتْ فَرَضَ اللَّهُ الصَّلاَةَ حِينَ فَرَضَهَا رَكْعَتَيْنِ ثُمَّ أَتَمَّهَا فِي الْحَضَرِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ عَلَى الْفَرِيضَةِ الأُولَى

The prayer was prescribed as consisting of two rak'ahs, the prayer in travelling remained the same, but the prayer at the place of residence was completed. (Zuhri said he asked 'Urwa why 'A'isha said prayer in the complete form during journey, and he replied that she interpreted the matter herself as 'Uthman did.)

أَنَّ الصَّلاَةَ أَوَّلَ مَا فُرِضَتْ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَأُتِمَّتْ صَلاَةُ الْحَضَرِ قَالَ الزُّهْرِيُّ فَقُلْتُ لِعُرْوَةَ مَا بَالُ عَائِشَةَ تُتِمُّ فِي السَّفَرِ قَالَ إِنَّهَا تَأَوَّلَتْ كَمَا تَأَوَّلَ عُثْمَانُ

The prayer was prescribed as consisting of two rak'ahs both when one was resident and when travelling. The prayer while travelling was left according to the original prescription and the prayer of one who was resident was enhanced.

فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ

"The first time the Salah was enjoined it was two Rak'ahs, and it remained as such when traveling, but the Salah while resident was made complete."

أَوَّلَ مَا فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَأُتِمَّتْ صَلاَةُ الْحَضَرِ

"The Salah was enjoined two Rak'ahs at a time, then the Salah when traveling remained like that, but the Salah while resident was increased."

فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ

"The prayer of the resident was enjoined on the tongue of your Prophet ﷺ, four (rak'ahs), and the prayer of the traveler is two rak'ahs, and the prayer of fear is one rak'ah."

فُرِضَتْ صَلاَةُ الْحَضَرِ عَلَى لِسَانِ نَبِيِّكُمْ ﷺ أَرْبَعًا وَصَلاَةُ السَّفَرِ رَكْعَتَيْنِ وَصَلاَةُ الْخَوْفِ رَكْعَةً

[AI] "The prayer was initially ordained with two units (rak'ahs). Then the prayer of travel (safar) was established with a shortened form, while the prayer of residence (hadar) was performed in its complete form." So I asked, "What was the reason for completing the prayer during travel?" He (Uthman) said, "It was interpreted (or understood) in this way as Uthman had also interpreted it."

«إِنَّ الصَّلَاةَ أَوَّلَ مَا فُرِضَتْ رَكْعَتَيْنِ فَأُقِرَّتْ صَلَاةُ السَّفَرِ وَأُتِمَّتْ صَلَاةُ الْحَضَرِ» فَقُلْتُ مَا لَهَا كَانَتْ تُتِمُّ الصَّلَاةَ فِي السَّفَرِ؟ قَالَ إِنَّهَا تَأَوَّلَتْ كَمَا تَأَوَّلَ عُثْمَانُ

[AI] The prayer was prescribed as two units, but the Messenger of Allah ﷺ added in the prayer of noon and left the prayer of travel as it is.

فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ فَزَادَ رَسُولُ اللهِ ﷺ فِي صَلَاةِ الْحَضَرِ وَتَرَكَ صَلَاةَ السَّفَرِ عَلَى نَحْوِهَا

Yahya related to me from Malik from Salih ibn Kaysan from Urwa ibn az-Zubayr that A'isha, the wife of the Prophet ﷺ said, "The prayer was prescribed as two rakas, both when settled and when travelling. Then the travelling prayer was kept as it was, and an increase was made in the prayer when settled. "

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ فُرِضَتِ الصَّلاَةُ رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ وَزِيدَ فِي صَلاَةِ الْحَضَرِ

[AI] She said, "The first thing that was obligated regarding prayer, whether in settled or traveling situations, is two units of prayer. Then the prayer was increased in settled situations, while it was simplified in traveling situations."

أَنَّهَا قَالَتْ «أَوَّلُ مَا فُرِضَتِ الصَّلَاةُ فِي الْحَضَرِ وَالسَّفَرِ رَكْعَتَيْنِ ثُمَّ زِيدَ فِي صَلَاةِ الْحَضَرِ وَأُقِرَّتْ فِي السَّفَرِ»

[AI] I heard Al-Sa'ib bin Yazid Al-Kindi, the son of the daughter of Al-Namir, saying, "Prayer was initially prescribed as two units of prayer, then it was increased during the Salah of Al-Hadar (residing) and the prayer of Al-Safar (travel) was made shorter."

سَمِعْتُ السَّائِبَ بْنَ يَزِيدَ الْكِنْدِيَّ ابْنَ أُخْتِ النَّمِرِ يَقُولُ «فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ رَكْعَتَيْنِ ثُمَّ زِيدَ فِي صَلَاةِ الْحَضَرِ وَأُقِرَّتْ صَلَاةُ السَّفَرِ»

"The Salah was enjoined two Rak'ahs at a time, then the Salah when traveling remained like that, but the Salah while resident was increased." (Using translation from Nasāʾī 455)

«فُرِضَتِ الصَّلَاةُ رَكْعَتَيْنِ فَأُقِرَّتْ صَلَاةُ السَّفَرِ وَزِيدَ فِي صَلَاةِ الْحَضَرِ»

"The prayer of the resident was enjoined on the tongue of your Prophet ﷺ, four (rak'ahs), and the prayer of the traveler is two rak'ahs, and the prayer of fear is one rak'ah." (Using translation from Nasāʾī 1441)

«فُرِضَتْ صَلَاةُ الْحَضَرِ عَلَى لِسَانِ نَبِيِّكُمْ أَرْبَعًا وَصَلَاةُ السَّفَرِ رَكْعَتَيْنِ وَصَلَاةُ الْخَوْفِ رَكْعَةً»

"The prayer of the resident was enjoined on the tongue of your Prophet ﷺ, four (rak'ahs), and the prayer of the traveler is two rak'ahs, and the prayer of fear is one rak'ah." (Using translation from Nasāʾī 1441)

«فُرِضَتْ صَلَاةُ الْحَضَرِ عَلَى لِسَانِ نَبِيِّكُمْ ﷺ أَرْبَعًا وَصَلَاةُ السَّفَرِ رَكْعَتَيْنِ وَصَلَاةُ الْخَوْفِ رَكْعَةً»

"عَنْ عَائِشَةَ قَالَتْ: فَرَضَ اللهُ - تَعَالَى- آيَةَ الصَّلَاةِ أَوَّلَ مَا فَرَضَهَا رَكْعَتَيْنِ ثُمَ أَتَمَّهَا لِلْحَاضِرِ، وَأُقِرَّتْ صَلَاةُ السَّفَرِ عَلَى الفَرِيضَةِ الأُولَى".