Is the prayer of one who chews tobacco in his mouth valid, and is the prayer of those led in prayer (ma'moom) behind an imam who chews it valid?

It is forbidden to use tobacco, whether by smoking or chewing. The prohibition is intensified when used during prayer, as it contradictsخشوع (devotional humility). Merely placing chewable tobacco in the mouth does not invalidate the prayer, unless it is accompanied by chewing or swallowing any dissolved particles, in which case the prayer becomes invalid. A smoker should not be appointed as an Imam if the congregants are not smokers; however, the prayer of the congregants behind him is valid. If the Imam's prayer becomes invalid due to chewing or swallowing, concealed from the congregants, the congregants' prayer is not invalidated.