Ata (may Allah have mercy on him) said: Ubayd bin Umayr (may Allah have mercy on him) and I came to Sayyidah Aishah (may Allah be pleased with her). She was at Bi'r Maymun, cleaning her teeth with a miswak, and the sound came from behind the curtain. She threw a cushion to us. He said: We asked her about a number of things, and we also asked about this verse: "Allah will not take you to account for what is idle in your oaths" [Surah al-Baqarah: 225]. We said: What is the idle oath (laghw)? She said: It is people's talk, such as: By Allah, we did such and such.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19938