In this sermon, the speaker emphasizes the power of the tongue and its potential for both life and death. He urges listeners to speak truthfully and to restrain themselves in conversation, allowing reason to rule over emotions. The speaker highlights the issue of disunity within the fellowship and how the indiscipline of the tongue can contribute to it. He references the book of Proverbs, which emphasizes the importance of thinking before speaking, listening to others, and avoiding gossip. The speaker also shares advice from his mother about considering the impact of our words on others before speaking.