Woah

I'm still piecing this together, so if anyone has any thoughts, I would appreciate hearing them.
Psalm 59: 12-13a For the sins of their mouths, for the words of their lips, let them be caught in their pride. For the curses and lies they utter Consume them in wrath, consume them till they are no more. This is very clear, and shook me up a little. David uses the words "sins of their mouths." i guess I can fool myself into thinking speech is a small thing, but here it is treated as being a very big deal.
Then, I read in Acts 8:6 When the crowds heard Phillip and saw the miraculous signs he did, they all paid close attention to what he said.
It seems like Phillips actions spoke much louder with the people. The signs convinced them to tune into the gospel and what he was saying.
If what we say is such a big deal, then our actions must really matter in God's eyes. I'm still puzzling through this one.