´It was narrated that 'Imran bin Husain said:` The Messenger of Allah said: "There is no vow to commit an act of disobedience or with regard to that which the son of Adam does not possess."
Related hadith on this topic
Explanation & Benefits
Hafiz Muhammad Ameen
For details, see 3823 H.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 3843
Hafiz Muhammad Ameen
However, if one makes a vow (nadhar), then in both cases it is prohibited to fulfill the vow. One will have to give expiation (kaffarah), as has been mentioned previously.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 3880
Maulana Ataullah Sajid
Benefits and Issues:
➊ A vow (nadhar) is made to please Allah, therefore if a person makes a vow to do something sinful, that vow is null and void and it is not permissible to fulfill it. For example: if someone vows that he will give more to one of his sons than to the others, or makes a vow to do something that is not, according to the Shari‘ah, a virtuous deed—for instance, a vow that “I will stand in the sun”—then he should not fulfill such a vow; instead, he should offer expiation (kaffarah) for it.
➋ If someone vows to offer something he does not own, for example: he vows to slaughter another person’s animal, then this is not valid. However, if he intends to purchase that animal and hopes that the owner will sell it, then after buying it, he may slaughter it.
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 2124