Is saying "A'udhu billahi minash-shaitanir-rajeem" (I seek refuge in Allah from the accursed Satan) before prayer with the intention of warding off Satan considered an innovation (bid'ah)?

Seeking refuge with Allah from Satan is a good and commanded act, as Allah the Almighty says: "And say, 'My Lord, I seek refuge in You from the incitements of the devils, and I seek refuge in You, my Lord, lest they be present with me.'" However, one should not persist in doing so before every prayer, as it has not been authentically reported from the Prophet (peace be upon him), and that might fall under the category of an added innovation (bid'ah idafiyyah). But when one feels intrusive whisperings (waswasah) during prayer, one should seek refuge with Allah and spit lightly to the left three times, as 'Uthman ibn Abi al-'As did with the devil named "Khanzab."