"for out of the abundance of the heart his mouth speaks"
He starts off by explaining with the understanding in their culture which was farming. If a tree is rotten from it's roots (the heart), do you think it will produce fruit or good leaves? No. On the other hand, if the tree is hearty and by a stream of flowing water and nutrients, it's heart will be very good. What kind of fruit will this tree produce? Amazing, luscious fruit good for eating. Likewise, a person's heart will produce good or bad fruit.
In conclusion, what is your heart producing? Think about your speech. What comes from your mouth? Are you building others up, or breaking them down with your words? Do you gossip about others? Jesus says he is the bread of life and He will give living water that never runs dry. The only way to be fed, is by reading and practicing God's word in your lives. An outflow of life and good fruit will come from your mouth.
Lord I ask you show me the places in my heart that need to be covered with your bread and water. Please reveal to me the words that I speak that aren't pleasing to you. Convict me of sin that keeps me from your blessings. If we think we don't sin then we are utter fools, but we should strive and strive to be more like you, having an abundant heart of love and compassion. Thank you Jesus for all that you have done, do and are. In Your name I pray Amen.