Bulugh al-Maram

Allah's Messenger (ﷺ) overtook 'Umar bin al-Khattab when he was with a party of riders of about ten and 'Umar was swearing by his father. Allah's Messenger (ﷺ) called them and said, "Verily! Allah forbids you from swearing by your fathers. Therefore, if anyone swears, he must swear by Allah or keep silent." [Agreed upon]

"Do not swear by your fathers, nor by your mothers, nor by the rivals (set up as equals with Allah); and do not swear by Allah except when you are speaking the truth."

Allah's Messenger (ﷺ) said: "Your oath will be about that matter which your adversary has required you to swear about so that he will believe you." In another narration: "An oath is to be interpreted according to the intention of the one who requested it (Al-Mustahlif)." [Muslim reported both narrations].

Allah's Messenger (ﷺ) said: "When you swear an oath and then consider something else to be better than it, make atonement for your oath and do the thing that is better." [Agreed upon]. A wording of al-Bukhari has: "Do the thing that is better and make atonement for your oath." In a narration by Abu Dawud: "Make atonement for your oath, then do the thing that is better." [The chains of narrators of both Ahadith are Sahih (authentic)].

"Allah's Messenger (ﷺ) said: "Whoever swears an oath, and then says: "If Allah Wills", he is not held accountable if he breaks it." [Ahmad and al-Arba'a reported it, and Ibn Hibban graded it Sahih (authentic)].

The Prophet's oath (ﷺ) used to be: "No, by Him Who turns (changes) the hearts." [Reported by al-Bukhari].

A desert Arab came to the Prophet (ﷺ) and said, "O Allah's Messenger, what are the major sins?" The narrator reported the Hadith and it contains: "The false oath." It contains also: I asked, "What is the false oath?" The Prophet (ﷺ) replied, "It is that (oath) by which one takes possession of the property of a Muslim person, while he is lying." [al-Bukhari reported it].

"Allah will not punish you for what is unintentional in your oaths (5:89)." She said: It (was sent down about such phrases as) a person's sayying: 'No, by Allah' and 'Yes, by Allah.' [al-Bukhari reported it (Mauquf, i.e. as a saying of 'Aishah). Abu Dawud reported it as Marfu' (attributed to the Prophet).]

Allah's Messenger (ﷺ) said: "Verily! Allah has ninety-nine Names concerning which he who retains them in his memory will enter Paradise." [Agreed upon]. at-Tirmidhi and Ibn Hibban listed the Names. However, investigations show that their listing is Idraj (an insertion) from one of the narrators [not from the words of the Prophet].

Allah's Messenger (ﷺ) said. "If one is done a kindness and [expresses his gratitude] to his benefactor by saying 'May Allah give you a good reward', he has fully expressed his appreciation." [at-Tirmidhi reported it, and Ibn Hibban graded it Sahih (authentic)].