Musnad Ahmad 1304:50

Muhammad ibn Bakr narrated to us, Ubayd Allah ibn Abi Ziyad informed us, Shahr ibn Hawshab narrated to us, from Asma bint Yazid, she said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever defends the flesh of his brother in his absence, it is a right upon Allah to free him from the Fire."