It is narrated from Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him) that he complained to the Messenger of Allah (peace and blessings be upon him) of whispering (waswasah) during prayer, and he (peace and blessings be upon him) said: "That is a devil called Khanzab. When one of you senses anything of him, let him spit (lightly) to his left three times and seek refuge in Allah from him."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8336