Is the prayer of a man in the desert valid if he prays in a direction other than the Qibla due to ignorance of the ruling?

Facing the Qibla (definition) is one of the conditions for the validity of prayer. Whoever is unsure of its direction should strive and investigate its direction, and then pray towards it. If he is unable to exercise ijtihad (definition) (independent reasoning), he should follow a mujtahid (qualified scholar) if he finds one. His prayer is valid, and he does not have to repeat it, even if it later becomes clear that he erred in facing the Qibla, because he fulfilled what he was commanded to do. As for one who prays without exercising ijtihad, he must repeat the prayer.