"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.''"
Jami` at-Tirmidhi Book 20, Hadith 18
← Previous Hadith 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)."

Jami` at-Tirmidhi Book 20, Hadith 17 Next Hadith → From this father (Ibn Umar) who said: "The Messenger of Allah (ﷺ) often would swear with this oath: 'No! By the Changer of the Hearts.'"

Jami` at-Tirmidhi Book 20, Hadith 19