Prayer: A Traveller Unaware of the Details Performing Tamam Prayers
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1345
A traveller who knows that he must perform qaṣr prayers but does not know some of its details – for example, he does not know that qaṣr prayers must be performed on an eight farsakh journey – then, in the event that he performs tamām prayers and realises this within the prescribed time for the prayer, he must, based on obligatory precaution, perform it again; and if he does not perform it again, he must make it up. However, if he realises after the time has expired, there is no obligation to make it up.