Making a vow to commit a sin
In the name of Allah, the most Beneficent, the most Merciful.
Saaiduna Imran Bin Hussain Radiallahu Anhu reported that the Prophet of Allah Sallallahu Alahi Wasalam said: "There should be no fulfilment of a vow to commit sin." (Sahih Muslim)
In the Hanafi Fiqh if someone made a vow to commit a sin like drinking alcohol or to kill someone the that vow would be considered invalid, hence, there will be no need to give a kaffarah (expiation). (Taqrir Tirmizi p.175 v.2)
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.