Sayyiduna Hakim bin Hizam (may Allah be pleased with him) said: It was said: O Messenger of Allah, which charity is best? He (peace and blessings be upon him) said: "Giving charity to a relative who harbours hidden enmity (in his heart)."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3113