Fulfilling others' oaths between obligation and recommendation
15-1-2014 | IslamWeb
Question:
Is it due on a person to abide by all he is asked to do if somebody says to him, "I swear by Allaah that you should do such and such for me," given that he frequently takes oaths even on insignificant matters and on things one may see as devoid of interest?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Indeed, to fulfill the oath of someone is encouraged. It is narrated on the authority of Al-Baraa’ ibn ‘Aazib 
that he said: “The Prophet, sallallaahu ‘alayhi wa sallam, ordered us to do seven things and forbade us from doing seven. He ordered us to follow funeral processions, to visit the sick, to accept invitations, to support the oppressed, to fulfill others' oaths, to return the greeting, and to say to someone who has sneezed, 'May Allaah Bestow His Mercy upon you,' if he says, 'Praise be to Allaah.' He forbade us to use silver utensils, to wear gold rings, to wear silk, Deebaaj (brocade), Qassi (linen clothes containing silk brought from an Egyptian town), and Istabraq (a kind of silk)." [Al-Bukhari]
It is further narrated on the authority of Abu Moosa Al-Ash‘ari that he heard the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, say: “Cursed is he who asks (another for something) by the Countenance of Allaah; and cursed is he who is asked (for something) by the Countenance of Allaah and withholds it from his asker so long as he does not ask for desertion.” [At-Tabaraani] [Hasan]
It is narrated on the authority of Jaabir ibn ‘Abdullaah that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: “Nothing should be asked by the Countenance of Allaah except Paradise.” [Abu Daawood]
It is narrated on the authority of Ibn ‘Abbaas 
that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: “He who seeks refuge with Allaah (from evil), then grant him refuge; and he who asks you by the Countenance of Allaah (for something), give it to him.” [Ahmad and Abu Daawood]
The majority of scholars view that the command entails recommendation to fulfill the oaths taken by others, as well as to answer the one who asks by the Countenance of Allaah.
The apparent meaning of the Hadeeth of Al-Baraa’ indicates that it is obligatory to help others fulfill their oaths. At the same time, mentioning it side by side with deeds that are not obligatory such as spreading the greeting of peace is proof that it is not obligatory.
What further confirms that it is not obligatory is that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, did not fulfill the oath of Abu Bakr As-Siddeeq . It is narrated on the authority of Ibn ‘Abbaas that once a man came to the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, and related a dream to him and Abu Bakr asked the Prophet to allow him to interpret it, The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, gave him permission. When he finished he said: “Let my father sacrifice his life for you, O Messenger of Allaah! Have I been right or wrong?” he said: “You have been right in part and wrong in part.” He said: “I swear by Allaah, O Messenger of Allaah, that you should tell me in which thing I have been wrong.” He, sallallaahu ‘alayhi wa sallam, said: “Do not swear.” [Al-Bukhari and Muslim]
In his commentary on Saheeh Muslim, An-Nawawi 
said: "This Hadeeth is proof that supports the opinion of the scholars who say that fulfilling others' oaths – which is enjoined in the authentic Hadeeths –is that which does not lead to apparent evil or difficulty and that otherwise it is not enjoined."
In his book Az-Zawaajir ‘An Iqtiraaf Al-Kabaa’ir, Ibn Hajar Al-Haytami said while speaking about major sins number 138 and 139, after mentioning the Hadeeths: "… but our Imaams did not consider this point and rendered both (asking by the Countenance of Allaah and failing to respond to such a question) disliked rather than unlawful or a major sin. The person is cursed in the Hadeeth for not responding to the request of the asker if the latter undergoes severe need. The wisdom behind stating the curse explicitly, is that the person is denied fulfillment of his request despite his need. It makes it more grievous if the person asks by Allaah the Almighty. Likewise, the asking person is cursed if he asks importunately and repeatedly by the Countenance of Allaah till he troubles the asked person and harms him. Thus both deserve the curse.
Allaah Knows best.