Is it permissible for the husband to break his fast in Ramadan due to the hardship and exhaustion of work? And is expiation (kaffarah) due from him? And must the pregnant wife who broke her fast make up the days (qadaa') in addition to offering expiation?

Fasting Ramadan (definition) is a great pillar [of Islam]; it is impermissible for a fasting person to break their fast due to probable thirst or fatigue. If they do break their fast, they must repent and make up the fast. A fasting person, by their intention to fast, becomes obligated to fast, even if they fear severe harm to themselves. In such a case, it is permissible for them to break their fast out of necessity, as Allah the Almighty says: "Allah does not burden a soul beyond its capacity" and "Allah does not intend to make any difficulty for you." The days that were broken must be made up after Ramadan and before the arrival of the next Ramadan, and it is recommended to hasten in making them up. As for pregnant and breastfeeding women, if they fear for themselves or their fetus/child, it is permissible for them to break their fast, and they only owe making up the fasts.