Colossians 4:5
Be wise in the way you live in front of outsiders [i.e., non-Christians], making the most of every opportunity.
Hebrews 2:1
So [then], we [Christians] should pay closer attention to the things we have heard, so that we do not drift away from [believing and practicing] them.
James 1:26
If anyone considers himself to be religious and yet does not keep a tight rein on his tongue, this person is self-deceived and his religion is worthless.
James 3:2-8
For we all make mistakes in many areas [of life]. If anyone does not make a mistake in what he says, he is a perfect person, capable of keeping a tight rein on his whole life also.