Ata bin Abi Rabah said: I and Ubayd bin Umayr al-Laythi were with Aishah (may Allah be pleased with her), when Ubayd bin Umayr asked about the saying of Allah, "Allah will not take you to account for what is vain in your oaths" [Surah al-Baqarah: 225]. She said: A person swears according to what he knows, then the matter turns out not to be so; there is no expiation for that.
Umar bin Qays narrated it this way, and he is not strong.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19941
Urwah bin al-Zubayr (may Allah have mercy on him) narrates from Sayyidah Aishah (may Allah be pleased with her) that she used to interpret this (verse) as follows: it is something a person swears upon, intending nothing but the truth by it, yet it turns out contrary to it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19942
Ibn Abi Najih (may Allah have mercy on him) narrates from Mujahid (may Allah have mercy on him) concerning this verse: a man swears that such-and-such a thing is so, while it is not so.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19943
Al-Hasan (may Allah have mercy on him) said concerning the saying of Allah Almighty, "Allah will not take you to account for what is vain in your oaths" [Surah al-Baqarah: 225]: a man swears about something but it is not so; for that there is neither expiation nor being taken to account. Rather, being taken to account is for (swearing) with knowledge.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19944
Al-Hasan (may Allah have mercy on him) said: A man says, "By Allah! I did not do it," when he had in fact done it forgetfully; that is nothing. It is a lie; let him seek Allah's forgiveness, and there is no expiation on him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19945