Answer:
(Fatwa: 533/450/B=1433)
Interest money is haram and malicious. It should be given to very poor and needy person without the intention of reward. It is not lawful to use it in the construction of toilet and latrine of the mosque.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
