While the lectionary readings aren't meant to be connected to each other, I am using Jesus harsh words to Peter as an example of what I will call "redemptive" use of the tongue and contrast that with James examples of "unredemptive" use of the tongue. Here are the readings:
Mark 8:27-3827 Jesus and his disciples went on to the villages around Caesarea Philippi. On the way he asked them, ‘Who do people say I am?’
28 They replied, ‘Some say John the Baptist; others say Elijah; and still others, one of the prophets.’
29 ‘But what about you?’ he asked. ‘Who do you say I am?’
Peter answered, ‘You are the Messiah.’
30 Jesus warned them not to tell anyone about him.
31 He then began to teach them that the Son of Man must suffer many things and be rejected by the elders, the chief priests and the teachers of the law, and that he must be killed and after three days rise again. 32 He spoke plainly about this, and Peter took him aside and began to rebuke him.
33 But when Jesus turned and looked at his disciples, he rebuked Peter. ‘Get behind me, Satan!’ he said. ‘You do not have in mind the concerns of God, but merely human concerns.’
34 Then he called the crowd to him along with his disciples and said: ‘Whoever wants to be my disciple must deny themselves and take up their cross and follow me. 35 For whoever wants to save their life[a] will lose it, but whoever loses their life for me and for the gospel will save it. 36 What good is it for someone to gain the whole world, yet forfeit their soul? 37 Or what can anyone give in exchange for their soul? 38 If anyone is ashamed of me and my words in this adulterous and sinful generation, the Son of Man will be ashamed of them when he comes in his Father’s glory with the holy angels.’
James 3:1-123 My friends, not many of you should become teachers. As you know, we teachers will be judged with greater strictness than others. 2 All of us often make mistakes. But if a person never makes a mistake in what he says, he is perfect and is also able to control his whole being. 3 We put a bit into the mouth of a horse to make it obey us, and we are able to make it go where we want. 4 Or think of a ship: big as it is and driven by such strong winds, it can be steered by a very small rudder, and it goes wherever the pilot wants it to go. 5 So it is with the tongue: small as it is, it can boast about great things.
Just think how large a forest can be set on fire by a tiny flame! 6 And the tongue is like a fire. It is a world of wrong, occupying its place in our bodies and spreading evil through our whole being. It sets on fire the entire course of our existence with the fire that comes to it from hell itself. 7 We humans are able to tame and have tamed all other creatures—wild animals and birds, reptiles and fish. 8 But no one has ever been able to tame the tongue. It is evil and uncontrollable, full of deadly poison. 9 We use it to give thanks to our Lord and Father and also to curse other people, who are created in the likeness of God. 10 Words of thanksgiving and cursing pour out from the same mouth. My friends, this should not happen! 11 No spring of water pours out sweet water and bitter water from the same opening. 12 A fig tree, my friends, cannot bear olives; a grapevine cannot bear figs, nor can a salty spring produce sweet water.