Urwah narrates from Sayyidah Aishah (may Allah be pleased with her): "At first the prayer was made obligatory as two rak'ahs each; then the prayer of the resident was increased, and the prayer of travel was kept as it was." The narrator says: I said: What is the matter with Aishah (may Allah be pleased with her) that she prays the prayer in full? He said: She interpreted (the matter) as Sayyiduna Uthman (may Allah be pleased with him) interpreted it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5432