whereas at Muzdalifah delayed combining is preferable, because it is easier for the people: stopping them on the road while they are travelling to Muzdalifah would cause hardship.
If someone were to ask: If the two options—combining in advance or delaying the combination—are equally convenient for a person, which is preferable?
The answer is that they say delayed combining is preferable, because the most it involves is delaying the first prayer beyond its prescribed time; and a prayer performed after its time due to an excuse is valid and sufficient. Combining in advance, however, entails praying the second prayer before its time begins, and a prayer offered before its time begins is invalid, even when there is an excuse. It is also the more cautious course, since some of those who permit combining do not permit combining in advance except at Arafah.
“If he combines them during the time of the first prayer, he must intend to combine them at its opening takbir, ……”
His statement, “If he combines them during the time of the first prayer, he must intend to combine them at its opening takbir,” means that combining during the time of the first prayer is subject to three conditions:
The first condition is intending to combine them at its opening takbir. This is based on the view that a traveller must intend to shorten the prayer, because combining means joining one prayer to another. Therefore, the intention to join them must encompass every part of the prayer, and so he must form this intention at the opening takbir of the first prayer. Thus, if he begins the first prayer without intending to combine them, then decides during the prayer to combine them, the combination is invalid, because he did not intend it at the opening takbir of the first prayer. Part of it was therefore devoid of the intention to combine, whereas combining means joining, and the joining must encompass the entire prayer. If he intends to combine them after concluding the first prayer, then it is invalid all the more so.
The correct view, however, is that it is not a condition to intend combining at the opening takbir of the first prayer. He may form the intention to combine even after concluding the first prayer, or even at the opening takbir of the second prayer, so long as the reason for combining remains present.