Is it permissible for a traveler to shorten the prayer – two rak'ahs instead of four for Dhuhr, Asr, and Isha – if he travels 80 kilometers daily, to and from, due to the length of the journey and the fatigue of travel that prevents him from performing the prayer in full?

The distance for qasr (shortening prayers) is approximately 83 kilometers, which is the distance at which Ibn Abbas and Ibn Umar would shorten prayers and break their fast. You are permitted to shorten the four-rak'ah prayer to two rak'ahs when going to and returning from your place of study, provided you have crossed the boundaries of your city. If you delay the prayer until you have entered the city and there is still time for it, then you must complete it. A condition for the permissibility of shortening prayers is that the journey must be lawful. Therefore, it is not permissible for a woman to travel without a mahram. A traveler on a journey of disobedience is not entitled to the concession, and this is the view of the majority of scholars. Although Imam Abu Hanifa and others hold the view that shortening prayers is permissible even on a prohibited journey, the view of prohibition is the most correct and cautious.