From his father (Ibn 'Umar) that the Prophet (ﷺ) heard 'Umar saying: "By my father, By my father!" So he said: "Verily Allah prohibits you from swearing by your father." So 'Umar said: "By Allah I did not swear by him after that, neither intentionally nor in narrating."
That the Messenger of Allah (ﷺ) came across 'Umar while he was on his mount, and he was swearing by his father. So the Messenger of Allah (ﷺ) said: "Verily Allah prohibits you from swearing by your fathers. So let the one who swears, swear by Allah, or be silent."
That Ibn 'Umar heard a man saying: "No by the Ka'bah" so Ibn 'Umar said: "Nothing is sworn by other than Allah, for I heard the Messenger of Allah (ﷺ) say: 'Whoever swears by other than Allah, he has committed disbelief or shirk.'"
"A Woman vowed to walk to the House of Allah, so the Prophet (ﷺ) asked about that, and he said: 'Verily Allah is in no need of her walking, order her to ride.'"
"The Prophet (ﷺ) passed by old man walking (while supported) between his two sons, so he said: 'What is the matter with this one?' They said: "O Messenger of Allah! He vowed to walk.' He said: 'Verily Allah [the Mighty and Sublime] is in no need of this person punishing himself.'" He said: "So he ordered him to ride."
That the Messenger of Allah (ﷺ) said: "Do not vow, for the vows does not prevent what is decreed at all, and it only causes the miser to spend (of his wealth)."
"I said:'O Messenger of Allah! I had vowed to perform I'tikaf in Al-Masjid Al-Haram for a night during the era of Jahiliyyah.' He said: 'Fulfill your vow.''"
"I heard the Messenger of Allah (ﷺ) saying: 'Whoever frees a believing slave, then Allah frees a limb from the Fire for each of his limbs, such that he frees his private parts in lieu of his private parts.'"