Musnad Ahmad 1210:1

Yahya ibn Ishaq narrated to us, he said: Ibn Lahi'ah narrated to us, he said: Yazid ibn Abi Habib narrated to us, from al-Harith ibn Ya'qub, from Ya'qub ibn al-Ashajj, from 'Amir ibn Sa'd, from Sa'd, from Khawlah, she said: I heard the Prophet, peace and blessings of Allah be upon him, say: "Whoever stops at a place and says: 'I seek refuge in the perfect words of Allah from the evil of what He created,' nothing shall harm him until he departs from it."