It is a major sin to take a false oath on something that has already been done or passed. For example, a person did not offer his salaat but when he was asked about it, he said: “I swear by Allah that I have offered my salaat.” Or, a person broke a tumbler and when asked about it he swears by Allah that he did not break it. There is no limit to the punishment that one will receive for taking a false oath intentionally. Nor is there any kaffarah for such a false oath. The only thing that a person can do is to continuously repent to Allah Ta’ala and seek His forgiveness. If a person takes a false oath mistakenly or due to some misunderstanding, it will be forgiven. There will be no kaffarah on such a false oath. For example, a person says: “I swear by Allah that so and so person has not arrived as yet”, and in his heart this person had the full conviction that this oath which he is taking is a true oath. Only later did he learn that at the time of taking the oath, that person had already arrived. Such a false oath will be forgiven and there is no kaffarah.
If an oath is taken for something that has not occurred as yet and would take place in the future, then if something contrary to this oath occurs, kaffarah will have to be given. For example, a person says: “I swear by Allah that it will rain today” or “that my brother will arrive today”. If it does not rain today or his brother does not arrive today, kaffarah will have to be paid.
A person says: “I swear by Allah that I will recite the Quran today.” It now becomes wajib on the person to recite the Quran. If he does not do so, he will be sinning and he will also have to pay kaffarah. A person says: “I swear by Allah that I will not do such and such work today.” It will not be permissible for him to do that work. If he does it, he will have to pay kaffarah.
A person takes an oath of committing a sin. For example, he says: “I swear by Allah that I will steal a certain item from a certain person”, “I swear by Allah that I will not offer my salaat today” or “I swear by Allah that I will never speak to my parents”. If a person takes oaths of this nature, it will be wajib upon him to break them and thereafter to pay kaffarah as well. If he does not do so, he will be sinning.
A person takes an oath that he will not eat a certain thing today. Thereafter, he forgetfully ate that thing and did not remember that he had taken an oath not to eat it. Alternatively, someone forced that thing into his mouth and forced him to eat it. In both cases, he will have to pay kaffarah.
In anger, a person takes an oath and says: “I will not give you a single thing.” Thereafter, he gives the person one cent or one rand. Even then the oath will be broken and kaffarah will have to be paid.