Musnad Ahmad 1156:165

Muhammad ibn Ubayd narrated to us, he said: Al-A’mash narrated to us, from ‘Amr ibn Murrah, from Yahya ibn al-Jazzar, he said: Some people from the companions of the Messenger of Allah (peace and blessings of Allah be upon him) entered upon Umm Salamah and said: "O Mother of the Believers, tell us about the secret of the Messenger of Allah (peace and blessings of Allah be upon him)." She said: "His secret and his public were the same." Then she regretted it and said: "I have disclosed the secret of the Messenger of Allah (peace and blessings of Allah be upon him)." She said: "So when he entered, I informed him, and he said: 'You have done well.'"