Musnad Ahmad 1138:2

Sulayman ibn Dawud al-Hashimi narrated to us, Isma'il—meaning Ibn Ja'far—narrated to us, al-'Ala'—meaning Ibn 'Abd al-Rahman—informed me, from Ma'bad ibn Ka'b al-Sulami, from his brother 'Abdullah ibn Ka'b, from Abu Umamah, that the Prophet (peace and blessings of Allah be upon him) said: "Whoever usurps the right of a Muslim man by his oath, Allah has made the Fire mandatory for him because of it, and has forbidden Paradise to him." A man said to him: "Even if it is a trivial thing, O Messenger of Allah?" He said: "Even if it is a twig of arak."