Sayyiduna Abu Umamah (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever seizes the right of a Muslim by means of his oath, Allah has forbidden Paradise to him and has made Hell obligatory for him." A man stood up and said: Even if it is something small? the Prophet (peace and blessings be upon him) said: "Even if it is a twig of the arak tree."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 794