Nafie' نافع مولى ابن عمر · The Book of Oaths and Vows

"If you swear an oath, then you see something better than it, then offer expiation for your oath, and do that which is better."

"The Prophet passed by a man who was circumambulating the Ka'bah, led by another man with a reign in his nose. The Prophet took him by the hand and commanded him to lead him by his hand." Ibn Juraij said: "Sulaiman told me that Tawus told him, from Ibn 'Abbas, that the Prophet passed by him when he was circumambulating the Ka'bah, and a man had tied his hand to another man with some string or thread or whatever. The…

"There is no vow to commit an act of disobedience, and no vow concerning that which the son of Adam does not possess."

"Whoever swears by a religion other than Islam, telling a lie, will be as he said, and whoever kills himself with something, he will be punished with it in the Hereafter, and there is no vow concerning that which a man does not possess."

It was narrated from Ibn 'Umar, that 'Umar had vowed to spend a night in 'Itikaf during the Jahiliyyah. He asked the Messenger of Allah about that, and he ordered him to perform the 'Itikaf.

"Umar had made a vow to spend a night in 'Itikaf in Al-Masjid Al-Haram. He asked the Messenger of Allah about that, and he ordered him to perform the 'Itikaf."