He replied:

Praise be to Allah. Scholars differ on this issue: some hold that offering the prayers in full is obligatory, while others hold that shortening them is obligatory. The correct view is that both are permissible. Whoever shortens them is not to be censured, and whoever offers them in full is not to be censured.

They also differ as to which is preferable. For someone who doubts whether shortening is permissible and wishes to err on the side of caution, offering the prayers in full is preferable. But someone to whom the Sunnah has become clear, and who knows that the Prophet (peace and blessings be upon him) prescribed only two units of prayer for the traveller, set no temporal or geographical limits on travel, and likewise set no fixed limit on a stay—whether three, four, twelve or fifteen days—should shorten his prayers.

This was the practice of a number of the early Muslims. Indeed, Masrūq was appointed to an office he would not have chosen, and he stayed for years, shortening his prayers. The Muslims stayed at Nahāwand for six months, shortening their prayers. They would shorten their prayers even though they knew that their business would not be concluded within four days or even longer. Likewise, after the conquest of Mecca, the Prophet (peace and blessings be upon him) and his Companions stayed for nearly twenty days, shortening their prayers. They stayed in Mecca for ten days during Ramadan without fasting. When the Prophet (peace and blessings be upon him) conquered Mecca, he knew that he would need to stay there for more than four days.

Since setting such a limit has no basis, a traveller continues to shorten his prayers for as long as he remains a traveller, even if he stays in one place for months. Allah knows best.

Written by:
Ahmad ibn Taymiyyah.