Prayer: Calculating the Start and End of the Journey and the Second Condition: Intention
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1266
The start of the eight farsakhs on one’s journey must be calculated from the point beyond which a person is deemed to be a traveller; this is usually the outskirts of a town. However, in some very big cities, it is possible that it is the outskirts of a particular area. The end of the journey of a traveller who intends to travel to a town or village that is not his home town (waṭan) is deemed to be his destination in that town or village, not the point of entry into that town or village.
Second condition: one must have the intention of travelling eight farsakhs from the commencement of his journey; i.e. he must know that he will travel eight farsakhs. Therefore, if he travels to a place that is less than eight farsakhs, and after reaching that place he makes the intention of going to a place that together with the distance he has already travelled totals eight farsakhs, then as he did not have the intention of travelling eight farsakhs from the commencement of his journey, he must perform tamām prayers. However, if he wants to travel eight farsakhs from that place, or, for example, he wants to travel a distance that together with the return journey totals eight farsakhs, he must perform qaṣr prayers.