1 Corinthians 8:7

8:7 But this knowledge is not shared by all. And some, by being accustomed to idols in former times, eat this food as an idol sacrifice, and their conscience, because it is weak, is defiled.

1 Corinthians 14:9

14:9 It is the same for you. If you do not speak clearly with your tongue, how will anyone know what is being said? For you will be speaking into the air.