Vows

It is narrated from Sayyiduna Abdullah (may Allah be pleased with him) that he said: "A vow (in reality) is an oath."

A similar narration is also reported from Sayyiduna Jabir (may Allah be pleased with him), that he too regarded a vow as being like an oath.

It is narrated from Ikrimah bin Khalid that a man vowed to slaughter a small herd of camels at the place 'Buwanah'. The Prophet (peace and blessings be upon him) asked him: "Did you make this vow, and say this, while there was in your heart some trace of a false notion from the affairs of the Jahiliyyah?" The man said: No. So he (peace and blessings be upon him) said: "Then fulfil your vow and slaughter them."

It is narrated from Abdullah bin Malik that the sister of Sayyiduna Uqbah bin Amir (may Allah be pleased with him) vowed that she would perform Hajj walking on foot with her hair loose (her head uncovered). So Uqbah (may Allah be pleased with him) asked the Prophet (peace and blessings be upon him) about this, and he (peace and blessings be upon him) said: "Command her to put on her head-covering (to cover her head), to ride, and to fast three days."
The imams of hadith and the jurists derive from this that a vow which involves violating a ruling of the Shari'ah or excessive hardship need not be fulfilled; rather, an expiation (such as fasting or charity) is to be given in its place, because Allah Almighty has no need of putting His servant to needless hardship.

Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated from Sayyiduna Sinan bin Abdullah al-Juhani (may Allah be pleased with him) that he told him that his paternal aunt al-Furay'ah (may Allah be pleased with her) came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah! My mother has died, and she owed a vow (nadhr) which she did not fulfil. If I fulfil it on her behalf, will that suffice for her? The Messenger of Allah (peace and blessings be upon him) said: "Tell me, if your mother had owed someone a debt and you paid it, would it not have been accepted from you?" She said: Yes! He (peace and blessings be upon him) said: "Then Allah, the Blessed and Exalted, has more right to that (that His debt be paid)."
Then she asked again: O Messenger of Allah! My mother has passed away, and she owed (a vow of) walking to the Ka'bah? He (peace and blessings be upon him) asked: "Are you able to walk on her behalf?" She said: Yes! He (peace and blessings be upon him) said: "Then walk yourself on behalf of your mother (and fulfil this vow)."

It is narrated from Sayyiduna Abdullah bin Badr (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Making a vow in any act of disobedience and defiance of Allah Almighty is not (legally) permissible or valid."

It is narrated from Sayyidah Fatimah bint Qays (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) dispatched an army and said: "If good news reaches me from them, I will praise Allah Almighty with a praise that fulfils the right of His praise and glorification." Then when news of victory and success reached him (peace and blessings be upon him) from the army, he (peace and blessings be upon him) praised the Exalted Lord with these words: 'Allahumma laka al-hamdu shukran, wa laka al-mannu fadlan' (O Allah, to You alone belongs all praise in gratitude, and Yours alone is the favour as grace and generosity).
At this, Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said: O Messenger of Allah! You had said: "If good news reaches me from them, I will praise Allah with a praise that is His due"? The Prophet (peace and blessings be upon him) said: "I said (fulfilling that right in these comprehensive words): 'Allahumma laka al-hamdu shukran, wa laka al-mannu fadlan' (O Allah, to You alone belongs all praise in gratitude, and Yours alone is the favour as grace and generosity)."