Swear by Allah?

Ques: If someone swore by the name of Allah that he knows someone who achieved XYZ and during/after the oath he realises that what he said is not true – will he be sinful and required to pay kaffarah? (Note that this case is meant like that it was not the intention to tell a lie.)

Ans: Walaikum Assalam.

No, he will not be required to pay kaffarah. As it is Yameen Lagwo (unintentional oath).
Allah says:

لَا يُؤَاخِذُكُمُ اللَّهُ بِاللَّغْوِ فِي أَيْمَانِكُمْ وَلَٰكِنْ يُؤَاخِذُكُمْ بِمَا كَسَبَتْ قُلُوبُكُمْ ۗ وَاللَّهُ غَفُورٌ حَلِيمٌ

Allah will not take you to task for that which is unintentional in your oaths. But He will take you to task for that which your hearts have garnered. Allah is Forgiving, Clement. (2:225)

But, one should not swear and even not say anything before confirming it. Prophet said,

كفى بالمرء كذبا أن يحدث بكل ما سمع

It is enough for a person to be a liar that he talks about everything he hears. (without confirming it.) – Muslim

And Allah knows best.

Answered by Yousuf
Sunniforum, 22nd Apr ’09