Answer:
(Fatwa: 1526/1083/L=1431)
For a vow to take place, it is necessary that the words of vow are uttered in a way that one hears it. The vow does not take place by only thinking in heart.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
