Musnad Ahmad 132:41

Ahmad ibn al-Hajjaj and Ya‘mar ibn Bishr narrated to us. Ahmad said: ‘Abdullah informed us. And Ya‘mar said: ‘Abdullah narrated to us, he said: Yahya ibn Ayyub informed me, from ‘Abdullah ibn Sulayman, that Isma‘il ibn Yahya al-Mu‘afiri informed him, from Sahl ibn Mu‘adh ibn Anas al-Juhani, from his father, from the Prophet, peace and blessings of Allah be upon him, who said: "Whoever protects a believer from a hypocrite who disparages him, Allah, Blessed and Exalted is He, will send an angel to protect his flesh on the Day of Resurrection from the fire of Hell. And whoever seeks to harm a believer with something by which he intends to disgrace him, Allah, the Exalted, will detain him on the bridge of Hell until he is cleared of what he said."