Explanation of the rule (if the cause ceases, the effect ceases) with an example

The questioner : It is a valid question. My question was the same as yours. Does the wisdom behind it mean facilitating matters for the Muslim? Suppose a Muslim is able to pray; is it not better for him to complete it?

The Shaykh : No, and may Allah reward you. We must distinguish between the wisdom of a thing and the cause of a thing, or the wisdom of the ruling and the cause of the ruling. If we know by some means that the cause of a certain ruling is such-and-such, then if the cause ceases, the ruling ceases. That is why the scholars of usul al-fiqh (the principles of jurisprudence) say: "The cause revolves with the effect in existence and absence; if the cause ceases, the effect ceases." A clear example for them is khamr (intoxicants). Everyone knows the cause of the prohibition of khamr, which is intoxication. If the khamr turns into vinegar, the cause is gone, so it becomes lawful after it was forbidden. Similarly, carrion is forbidden to eat. If it turns into another substance, you look at that substance: is it lawful or forbidden in the Shari'ah? It is well known to you all that carrion, due to natural factors like the sun, wind, rain, and changes in the weather, turns into salt. Do we look at the origin of this salt and forbid it because its origin was forbidden? Or do we say no, salt is lawful? We say: Yes, the cause has ceased, which was that it was carrion and dead, and it has turned into something else entirely. When we know the cause of a thing, we then say: "If the cause ceases, the effect ceases." What is the cause of the command to shorten the prayer? Is it relief and facilitation, as you said? Or is it something else?
We say: The cause is not facilitation for people, meaning that if there is no hardship, one completes the prayer. No, rather, as the scholars rightly say, "The cause is the likelihood that travel involves hardship." The likelihood that something involves hardship is different from the case where the cause is the hardship itself. If the cause were the hardship, then a person who travels and rests—some people, especially if they are poor and happen to stay in a hotel where they might not see the room, and they rest while traveling—this is facilitation for him. Does he shorten or complete? If we said the cause of the command to shorten is hardship, then the cause has ceased here, so the effect ceases. But the cause is not the hardship, but the likelihood of hardship. This is a matter that many people feel clearly. The difference is this: you may travel and fast in Ramadan, for example, and say, "By Allah, I feel completely comfortable." But then, during the trip, you feel the need for a drink, for example. Here the difference appears between travel being a likelihood of hardship. Therefore, the Muslim should adhere to the ruling as it came, as long as it is not conditioned on hardship.
Add to this that if it were a choice, the Wise Lawgiver would not have distinguished between prayer and fasting. In prayer, He commanded shortening, and in fasting, He explicitly said, as in Sahih Muslim: . Similarly, it came in the two Sahihs from the hadith of Anas ibn Malik and others that the Prophet (peace and blessings be upon him) traveled in Ramadan, and many of the Companions traveled with him, including Anas, who said: This is the ruling for fasting in Ramadan: there is a choice. As for prayer—as you heard just now—... when the Messenger went out for the Farewell Pilgrimage, from the moment he left the city, he shortened until he returned to it. All his travels were like this; he did not complete the prayer except once, and his Companions shortened with him.
In addition to this, there are hadiths that confirm the obligation of shortening, including .