Musannaf Ibn Abi Shayba 13:2190

Abu Bakr narrated to us, he said: Yunus narrated to us, he said: Layth ibn Sa’d narrated to us, from Hisham ibn Sa’d, from Muhammad ibn Zayd ibn al-Muhajir ibn Qunfudh, from Abu Umamah al-Ansari (may Allah be pleased with him), from Abdullah ibn Unays, from the Prophet (peace and blessings of Allah be upon him), who said: "No swearer swears an oath of patience (falsely) by Allah, and inserts into it [something] like the wing of a mosquito, except that it will be a black spot in his heart until the Day of Resurrection."