بسم الله الرحمن الرحيم
(Fatwa: 181/164/SN=02/1437)
If any non-Muslim is extremely poor and distressed then you may support him from interest money on his family functions or at the time of need. If a non-Muslim is rich then it is not allowed to give him interest money in any way. Interest money can only be given to extremely distressed and destitute people. It is not lawful for a Muslim to participate in the religions festivals of non-Muslims or give him gift at such occasions though it is from halal money.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband