Question Answer
In the Name of Allah, the Most Merciful and Compassionate
It is not disbelief to swear by Allah Most High in a lie. It is, however, amongst the most egregious major sins.
The Messenger of Allah (may Allah bless him and give him peace) said, “The major sins are associating partners with Allah, false oaths, disobeying the parents, and killing a soul.” [Bukhari]
False oaths mentioned in the above narration refer to an oath taken by Allah Most High in which one knows that they are lying. One must repent from such a sin.
Conditions of a Sound Repentance
However, for the repentance to be sincere and sound, one must meet the following conditions:
(1) Sincere remorse over the sin
(2) Immediately abandoning the sin
(3) Having a firm resolve never to repeat the sin
[Nawawi, Riyadh al-Salihin]
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani