When the king of Egypt was told that the people had fled, the mind of Pharaoh and his servants was changed toward the people, and they said, “What is this we have done, that we have let Israel go from serving us?” - Exodus 14:5 (ESV)
In the verse above, the word translated "mind" is the same word translated as "heart" in Deuteronomy 6:5. This word is most often translated as "heart". It is a word that is used to describe the inner life of a person, the seat of their faculties for thinking, feeling, and choosing. It is the notion of a self.
We have said that living for God with our heart involves the internal workings of our person. That is, how our thinking, desiring, and choosing interact and integrate with each other. For they surely can’t be completely disconnected in any real sense. How we think involves our understanding, our interpretations, our beliefs, and so on. These aspects of ourselves can’t help but influence what we desire since our thinking provides the why. And our choices can’t help but be influenced since our choices are rooted in certain beliefs about what will result. And those beliefs require thinking.
Understanding the Heart
In general, the term "heart" in Hebrew is a broad term used 228 times in the Old Testament. Many of the uses correspond to those that we would recognize today. Pharaoh is described as having a change of heart in Exodus 14:5, which is to say that he regretted sending away the Israelites. We can sympathize with the experience of feeling confident in a decision one moment only to regret it the next.
The term "heart" refers to the constellation of thoughts, desires, and choices which all interact with each other. In the case of Pharaoh, his thoughts seem to have changed from interpreting the expulsion of the Israelites as necessary to unnecessary. Together with this, his desire to be rid of Israel conflicted with his desire to retain their labor and Egypt's power over them.
Proverbs 21:25 says, "The desire of the sluggard kills him, for his hands refuse to labor." I believe this helps us immensely in understanding how to live for God with our hearts. When Pharoah had a change of heart, his desire to be rid of the troublesome Israelites was overruled by his desire to retain their labor. Because of this, Pharoah would not listen to reason. His nation had been decimated, yet he would not be denied. Pharoah seems to believe at that moment that getting the Israelites back was absolutely essential. His desire was overwhelmingly strong, and so Pharaoh sent his army after them. Pharaoh's desire killed him.
Why is this? Because Pharaoh's heart was dysfunctional. There can be no other word for it. No one who reads Exodus 7-10 could argue that it made sense for Pharaoh to persist, and yet he did. Pharoah did not make the decision from a position of sense because, in a very real sense, none of us makes any decision from a purely logical standpoint. In fact, this is impossible.
What do I mean? I mean that human beings do not function purely at the level of logic. Our operations occur at the level of the heart. Our cognition, affection, and volition are all inseparably interrelated, interactive, and interdependent. Our living cannot be reduced to mere logical calculations.
We experience every moment of our lives from within a matrix of thoughts, interpretations, beliefs, ideas, notions, hopes, fears, desires, expectations, intentions, decisions, and choices. We are complicated creatures.
An Ongoing Work
So when we talk about living for God with our heart, we might be helped in understanding it by considering what proportion of our inner workings are devoted to rightly understanding, interpreting, believing, desiring, prioritizing, worshipping, hoping in, following, obeying, honoring, and loving God. If we consider how much our heart is taken up by competing thoughts, desires, and intentions compared to God, we can more easily see what it would look like to live for him with our heart.
There is no denying that this idea is at once simple and profound. God should be on the throne of our hearts. He should be our prize jewel. Yet we find in ourselves that our hearts are dynamic. Things change. Intentions lose steam, beliefs fade, interpretations become skewed, and desires compete. What does it mean to live for God with our hearts? To do the work it takes to keep our hearts calibrated toward him and not allow ourselves to drift. Living for God with our hearts is, in many ways, captured in the simple and common biblical command to stand firm.
But standing firm does not totally cut it, because our hearts’ dynamism is not an inherently bad thing. The key is to leverage the dynamic nature of our heart for good: for right belief integrated with right desires and right choices. This takes work, but the payoff is worth it because to live for God with our heart cannot be fully understood without thinking in terms of holiness.
This continued work seems to trip up some people. It is my perception, broadly speaking, that some saints full of love and good deeds in their early years find their zeal waning in later years. Anecdotally, I have seen enough exceptions to this to know it is not necessary even if it is common.
There seems to be a notion out there that at some point you reach a level where you can essentially retire and coast. All that you have done in previous years works like a spiritual retirement account. Work today is no longer necessary because I can rely on the efforts I made many years ago. The problem with this thinking is that rest for the saints doesn’t come until they are dead or Jesus returns. We don’t love God for thirty years and do our own thing for the last ten. We don’t live for him for most of our lives only to coast at the end.
Paul makes a point to remark that he fought the good fight and ran the race until he finished it. He was not done as long as he was here. He was done when he inherited the crown of righteousness laid up for him in heaven. Rest is not for this life. Rest is for the next. If we misunderstand this concept, we will have a hard time rightly ordering our hearts to live for God through Christ.