Musannaf Ibn Abi Shayba 21:57

Al-Fadl ibn Dukayn narrated to us, he said: Yunus ibn Abi Ishaq narrated to us, from al-Minhal ibn ‘Amr, he said: Sa‘id ibn Jubayr narrated to me, from Ibn ‘Abbas, he said: If you come to a formidable ruler whom you fear will assault you, then say: "Allah is the Greatest, Allah is mightier than all of His creation together, Allah is mightier than what I fear and dread. I seek refuge in the One besides whom there is no god, the One who holds the seven heavens from falling upon the earth except by His permission, from the evil of Your servant so-and-so, and his soldiers, his followers, and his partisans among the jinn and mankind. O Allah, be a protector for me from their evil. Majestic is Your praise, mighty is Your protection, blessed is Your name, and there is no god other than You." (Say this) three times.