Is it permissible for a sick person to break their fast in Ramadan if their illness causes slight or moderate pain, by analogy with a traveler who is permitted to break their fast without obvious hardship?

A traveler is permitted to break their fast and shorten prayers (qasr) if they cover the distance of qasr (approximately 83 km); this is because travel is presumed to entail hardship. As for the sick person, they are not permitted to break their fast unless fasting becomes difficult for them, according to the majority of scholars. The difference between the two is that in travel, the presumption of hardship was considered—meaning long-distance travel—whereas in illness, no specific criterion was considered due to the variation in illnesses, which of them are harmful to fasting and which are not. Instead, the wisdom behind the ruling, which is the fear of harm, was considered.