What is the ruling on swearing a false oath to prevent one's husband from falling into debt, and is repentance or expiation obligatory?

The false oath, or "al-Yameen al-Ghamoos," is one of the major sins that immerses its perpetrator in sin and incurs God's wrath. This is based on what Al-Bukhari narrated from the Prophet, peace and blessings be upon him, who said: "(The) major sins (are): associating partners with Allah, disobedience to parents, killing a soul, and al-Yameen al-Ghamoos (the false oath)." And as stated in the Hadith (definition): "Whoever takes a false oath to unlawfully seize the property of a man will meet Allah, and He will be angry with him." This is in confirmation of Allah's saying: "Indeed, those who exchange the covenant of Allah and their oaths for a small price - those will have no share in the Hereafter, and Allah will not speak to them or look at them on the Day of Resurrection, nor will He purify them; and for them is a painful punishment."

Whoever has sworn falsely must repent to Allah with sincere repentance, showing remorse and resolving never to return to such an act again. This false oath has no expiation according to many scholars, because it is too grave to be expiated. This is what the majority of scholars, including Imam Ahmad, and the view of most scholars like Ibn Mas'ud, Malik, and others, have conveyed. However, some, like Ash-Shafi'i, hold that it does have expiation.

As for the money that was taken, if it was spent on essential necessities, there is no harm in it. However, if it was an extravagance exceeding customary expenditure, it must be returned to the husband, even without his knowledge.