Amongst the things that Allah has commanded to safeguard is oaths. When He mentioned the expiation of breaking oaths, He said,
“That is the expiation for breaking oaths when you have sworn them. Keep your oaths.” (al-Maidah 5:89)
People frequently make oaths and the consequences of breaching them vary: sometimes it will be the expiation for breaking oaths, other times a severe expiation is required and at other times it requires divorce or the like to take effect. Faith has entered the heart of a person who takes care of his oaths.
The Salaf would carefully safeguard their oaths. Some of them would never take an oath by Allah, others would be so guarded that they would give expiation for oaths they thought they had broken. Imam Ahmad, on his death bed, enjoined that the expiation for breaking oaths be given saying, ‘I think I might have broken an oath that I made.’
It is reported that when Ayyub, may Allah’s peace and blessings be upon him, passed by any two people swearing an oath by Allah, he would go an give expiation on their behalf lest they sin without realising it. This is why when he made an oath to lash his wife one hundred times, Allah granted him leeway [Mentioned in His saying, “Take a bundle of rushed in your hand and strike with that and do not break your oath.” (Sad 38:44)] because of his safeguarding his oaths and the oaths of others. The scholars have differed as to whether this leeway applies to others besides Ayyub.
Yazid ibn Abi Habib said, ‘It reached me that, amongst the carriers of the Throne, there is one whose eyes shed tears that flow like rivers. Then when he raises his head, he says, “Glory be to You, You are not feared as befits you.” Allah says, “Yet those who make oaths in My name falsely do not know this!”
A severe threat has been recorded concerning taking false oaths. Frequent oaths in the name of Allah, or false oaths in His name, arise from ignorance of Allah and lack of reverence in the heart.
The Legacy of the Prophet Ibn Rajab Al-Hanbali p 26-28