Sayyidah Aisha Siddiqa (may Allah be pleased with her) narrates: The prayers for travel and residence were made obligatory in the form of two, two rak‘ahs. The Prophet (peace and blessings of Allah be upon him) continued to perform two, two rak‘ahs (then later the number of rak‘ahs in the prayers was increased, but) the Fajr prayer was left as it is because of its lengthy recitation. The Maghrib prayer was left as it is because it is the witr (odd-numbered prayer) of the day.