Nasai

(1) The meaning of the Messenger of Allah (sallallahu alayhi wa sallam) is that Allah, the Exalted, has temporarily excused the obligatory fast from the traveler, so what then of the voluntary fasts—there is even more reason for exemption—therefore, you may eat. This does not mean that one should not observe voluntary fasts while traveling.

(2) “The fast and half the prayer.” However, there is a difference between the two. The obligatory fast must be made up later, and this is an agreed-upon issue. But the half of the prayer that is excused is permanently excused, meaning its make-up (qada) does not have to be performed.

(3) “Is excused.” But this does not mean that the traveler cannot fast or cannot perform the full prayer; rather, it is dependent on his own choice. This concession is in the sense of a dispensation (rukhsah).

(4) Not every prayer is excused by half, but only those prayers which are four units (rak‘ah): Dhuhr, ‘Asr, and ‘Isha. The other two prayers must be performed in full.