What is the ruling on shortening and combining prayers for a resident in a country other than his own?

It is not permissible to shorten prayers (qasr) except for a long-distance traveler. If he arrives in a country and intends to stay there for four days or more (some say fifteen days), then he is a resident and is not entitled to combine prayers (jam') or shorten them. If he shortens them, his prayer is invalid, and similarly, the second prayer of the two combined prayers in jam' al-taqdim (combining by bringing the second prayer forward). However, if he combines by jam' al-ta'khir (combining by delaying the first prayer to the time of the second), his first prayer is a make-up prayer (qada'), and he is not obligated to make it up.

He must re-perform the invalid prayers, even if they are numerous. This is the opinion of the majority of scholars.

There is another opinion that permits combining and shortening prayers for someone who arrives in a country and does not intend absolute residence, but rather temporary residence, such as for study. The combining would only be between Dhuhr and Asr, and Maghrib and Isha, and it is not permissible to combine Fajr with any other prayer. This opinion contradicts the opinion of the majority.