Allah Almighty says: {Allah will not hold you accountable for your unintentional oaths, but He will hold you accountable for your deliberate oaths. The expiation thereof is to feed ten needy people from what you normally feed your own family, or to clothe them, or to emancipate a slave. However, if someone cannot afford it, then he must fast for three days. That is the expiation for breaking your oaths. But be mindful of your oaths.} [Surat al-Mā’idah: 89]
1719/1 - ‘Ā’ishah (may Allah be pleased with her) reported: “This verse: {Allah will not hold you accountable for your unintentional oaths} was revealed with regard to people’s common statements: No, by Allah, and yes, by Allah.” [Narrated by Al-Bukhāri]
An idle oath is the oath that a person utters by his tongue and does not really mean.
1) It shows the mercy of Allah Almighty towards His servants, as He does not take them to task for the oaths they unintentionally utter without real intent. He does not oblige them to fulfill those oaths.
2) It draws the attention to the Shariah rule that it is the intention that matters in words and contracts.
3) The Prophet’s Sunnah goes hand in hand with the Noble Qur’an, explaining it and clearing any vagueness therein.