Mukhtasar Muslim

It is narrated from Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) that both in residence and on a journey, two rak'ahs were prescribed as obligatory, then the prayer during travel remained as it was, but the prayer during residence was increased. Zuhri (the narrator) said: I asked 'Urwah (may Allah be pleased with him), "Why did Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) perform the full prayer during travel? (That is, according to her, only two rak'ahs were obligatory.)" He replied: Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) interpreted it in the same way as Sayyiduna 'Uthman (may Allah be pleased with him) did (i.e., shortening the prayer during travel is a concession, and performing the full prayer is permissible).