What are the rulings regarding combining and shortening prayers for a traveler residing in Egypt, who works on a temporary project in Saudi Arabia, where he travels weekly from Egypt to Riyadh on Saturdays and returns to Egypt on Thursdays?

Shortening and combining prayers for a traveler are not obligatory but rather a concession. It is permissible to combine Maghrib and Isha prayers and shorten Isha prayer on an airplane during travel. One should pray standing, and perform bowing and prostration if possible; otherwise, the prayer should be delayed until arrival. If Riyadh is your place of work and you intend to reside there for more than four days, the ruling of travel ceases for you, and you complete the prayer immediately upon your arrival. When returning to Cairo, it is permissible to shorten Asr prayer on the airplane if standing, bowing, and prostrating are difficult, in which case the prayer is delayed until arrival and completed as four rak'ahs. Shortening prayers is not permissible in the hometown (Cairo) upon returning to it; the ruling of travel ceases, and prayers are completed. Do not avail yourself of concessions in the airport of the city where you reside unless the airport is outside of it.