The Isti`adhah cleanses the mouth from the foul speech that it has indulged in. It also purifies the mouth and prepares it to recite the speech of Allah. Further, the Isti`adhah entails seeking Allah's help and acknowledging His ability to do everything. The Isti`adhah also affirms the servant's meekness, weakness and inability to face the enemy of his inner evil, whom Allah alone, Who created this enemy, is able to repel and defeat. This enemy does not accept kindness, unlike the human enemy. There are three Ayat in the Qur'an that affirm this fact. Also, Allah said,
[إِنَّ عِبَادِى لَيْسَ لَكَ عَلَيْهِمْ سُلْطَـنٌ وَكَفَى بِرَبِّكَ وَكِيلاً ](Verily, My servants (i.e. the true believers of Islamic Monotheism) ـ you have no authority over them. And sufficient is your Lord as a Guardian.) (17:65).
We should state here that the believers, whom the human enemies kill, become martyrs, while those who fall victim to the inner enemy - Satan - become bandits. Further, the believers who are defeated by the apparent enemy - disbelievers - gain a reward, while those defeated by the inner enemy earn a sin and become misguided. Since Satan sees man where man cannot see him, it is befitting that the believers seek refuge from Satan with Whom Satan cannot see. The Isti`adhah is a form of drawing closer to Allah and seeking refuge with Him from the evil of every evil creature.