Here "dung on your faces" stands for disgrace. AT: "I will most certainly put you in deep disgrace; it will be as bad as if I had spread dung on your faces" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "festivals" stands for the animals that the priests offered in sacrifice at the Israelite festivals. "The dung" probably refers both to the dung that was produced by the animals just before they were slaughtered for sacrifice, and to the dung that was found inside the animals when their bodies were cut apart before being sacrificed. Temple workers had to transport this dung to a place outside of the temple, and probably outside of Jerusalem. (See: [[rc://en/ta/man/translate/figs-metonymy]])
This difficult expression can be translated as "God will take you away with it," that is, with the dung. This expression continues the same metaphor of slaughtering animals for sacrifice, and it can be put in active form. AT: "they will throw you on the dung pile; God will make sure that they take you away when they remove all the dung" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# he will take you away with it
Possible meanings of this expression are 1) God will punish the unfaithful priests by killing them and causing their bodies to be carried away on the piles of animal dung, or 2) God will punish the unfaithful priests in such a horrible way that it will be as if their bodies had been carried away with the animal dung. (See: [[rc://en/ta/man/translate/figs-metaphor]])