The Prophet (may Allah's peace and blessings be upon him) recited Sūrat At-Tīn, which is a short Sūrah, in the first Rak‘ah of the ‘Ishā prayer, because he was on a journey. While traveling, one should be keen on making things easier because of the hardship of traveling. Even though the Prophet (may Allah's peace and blessings be upon him) was on a journey, he didn't abandon what evokes humility and attentiveness of the heart in prayer when listening to the Qur'an, which is beautifying one's voice with the recitation of the Qur'an in prayer.