Allah's Messenger (ﷺ) said: "Whoever amongst you swears, (saying by error) in his oath 'By Al-Lat and Al- Uzza', then he should say, 'None has the right to be worshipped but Allah.' And whoever says to his companions, 'Come let me gamble' with you, then he must give something in charity (as an expiation for such a sin)." (See Hadith No. 645)
Sahih al-Bukhari Book 78, Hadith 134
← Previous Hadith Mu`adh bin Jabal used to pray with the Prophet (ﷺ) and then go to lead his people in prayer. Once he led the people in prayer and recited Surat-al-Baqara. A man left (the row of the praying people) and offered (light) prayer (separately) and went away. When Mu`adh came to know about it, he said. "He (that man) is a hypocrite." Later that man heard what Mu`adh said about him, so he came to the Prophet and said, "O Allah's Messenger (ﷺ)! We are people who work with our own hands and irrigate (our farms) with our camels. Last night Mu`adh led us in the (night) prayer and he recited Sura-al-Baqara, so I offered my prayer separately, and because of that, he accused me of being a hypocrite." The Prophet called Mu`adh and said thrice, "O Mu`adh! You are putting the people to trials? Recite 'Washshamsi wad-uhaha' (91) or'Sabbih isma Rabbi ka-l-A'la' (87) or the like."

Sahih al-Bukhari Book 78, Hadith 133 Next Hadith → that he found `Umar bin Al-Khattab in a group of people and he was swearing by his father. So Allah's Messenger (ﷺ) called them, saying, "Verily! Allah forbids you to swear by your fathers. If one has to take an oath, he should swear by Allah or otherwise keep quiet."

Sahih al-Bukhari Book 78, Hadith 135