Musannaf Ibn Abi Shayba 3:3198

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Hajjaj, from 'Awn, from Asma, who said: "Whoever recites 'Say, He is Allah, [who is] One' (Surah al-Ikhlas) and the two 'Seekers of Refuge' (Surah al-Falaq and Surah an-Nas) on Friday seven times while in his sitting position, he will be protected until the same time [next week]."