The ruling on the imam saying a word other than from the Qur'an during the prayer

Question : He says: Honorable Shaykh, if the imam slips up while the one behind him corrects him in his recitation, and the imam says a complete word other than from the Qur'an, such as saying "good" or "yes," does his prayer become invalid because of this?

Answer : The imam will not say that except as a slip of the tongue, and if it is a slip of the tongue, it does not harm, because it is without intention. As for if he says it intentionally, his prayer becomes invalid, because