I have posted several times about the condition of our heart and how it connects to our decisions, actions, thoughts, etc. Our actions, including our words will reflect our heart and what is inside. It is not a completely accurate gauge as there can be things that impact how others perceive us or things that can hinder our communication from accurately reflecting our heart, but it is a tool we can use to evaluate both our own heart and that of others. (Be careful about judging others by this tool alone though!)
The verse makes it clear that there is a connection between our hearts and what we treasure, but it leaves a question that we should ponder.
Does your heart lead you to what you treasure, or does what you treasure affect your heart?
“Where your treasure is” is commonly interpreted as referring to the things we value. That means the verse could be read as “Those things we value and focus on affect our heart.” I think that is true, but if we consider the heart first it could be said that “The condition of our heart affects what we value and focus on.”
Scripture is pretty clear that our heart is key to our walk with God and our beliefs.
Do you think our heart leads our focus, or our focus leads our heart? Do we need to have a clear answer, or is it okay to just accept that both the heart and our focus are important?