Aisha said, "Prayer was originally prescribed as two rakahs whether at home or while traveling. The traveler's prayer was left as it was, and the prayer at home was increased."
أنها قالت: فرضت الصلاة ركعتين ركعتين في الحضر والسفر، فأقرت صلاة السفر، وزيد في صلاة الحضر.
Malik narrated it in "Shortening the Prayer while Traveling" (8) from Salih bin Kaysan, from Urwa bin Zubayr, from Ayesha, as mentioned.Bukhari narrated it in "The Prayer" (350) from Abdullah bin Yusuf, and Muslim narrated it in "The Prayer of Travelers" (685) from Yahya bin Yahya, both of them from Malik with the same wording.Both of them also narrated it through the hadith of Sufyan, from Zuhri, from Urwa, from Ayesha, who said, "When the prayer was first made obligatory, it was two units. The travel prayer was kept as it was, while the prayer for residence was made complete."Zuhri said, "I asked Urwa, 'Why does Ayesha pray in full?' He said, 'She interpreted it as Uthman interpreted it.'" Sahih Bukhari (1090).Ibn Khuzayma (944) and Ibn Hibban (2738) both narrated it through the route of Mahbub bin Hasan, from Dawud bin Abu Hind, from Shaybi, from Masruq, from Ayesha, and they added, "When the Messenger of Allah ﷺ settled in Madinah, two more units were added to the prayer for residence, while the Fajr prayer was left as it was because of the length of its recitation, and the Maghrib prayer was left as it was because it is the odd prayer of the day."Its chain is hasan because of Mahbub bin Hasan, who is Muhammad bin Hasan bin Hilal bin Abu Zaynab, Abu Jafar or Abu Hasan, whose nickname is Mahbub. There is disagreement about him, though his hadith is hasan. Bukhari included his narrations paired with another narrator.As for the meaning of Urwa's statement, "She interpreted it as Uthman interpreted it," the majority said that the meaning of their interpretation is that they both viewed shortening the prayer as permissible, not obligatory. Other views have also been mentioned. Nawawi said this in Khulasa (2/725).As for what was reported from Uthman as a raised hadith, "Whoever settles down in a town should pray the prayer of a resident," it is a daif hadith.Imam Ahmad narrated it (443) from Abu Saeed, meaning the freedman of Banu Hashim, who said, Ikrima bin Ibrahim Bahili told us, Abdullah bin Abdul-Rahman bin Abu Dhubab told us, from his father, that Uthman bin Affan prayed four units at Mina, and the people objected to this, so he said, "O people, I have had a household in Makkah since I arrived, and I heard the Messenger of Allah ﷺ say," and he mentioned the hadith.In it is Ikrima bin Ibrahim Bahili. Hafiz reported in Tajeel from Husayni that he said, "He is not well known."Abu Zura said, "I do not know his status," but Hafiz followed this up by saying that he is "well known, his status being known," thinking that he was Ikrima bin Ibrahim Azdi. He then quoted the statements of the scholars regarding the weakening of Azdi, and said, "One should look into whoever attributed him to Bahila."I say, in either case, whether he was Bahili or Azdi, the chain is daif.Also in the chain is Abdul-Rahman bin Abu Dhubab, whom no one deemed reliable except Ibn Hibban, so he is at the rank of "acceptable" according to Hafiz.Among Uthman's interpretations is what he himself explained, that the prayer is only shortened by one who carries provisions and water skins, and who unloads and then sets out again.Tahawi mentioned this in his commentary (1/426), and he also mentioned other interpretations there.See for more Ahkam Safar wa Iqama (49) by Sheikh Islam bin Taymiya, may Allah have mercy on him.Its summary is what Nawawi said, that Uthman
viewed shortening the prayer as permissible, not obligatory.The hadith of Ayesha is contradicted by what comes next from Ibn Abbas.