Recently I found myself at a fairly large gathering of people and was amazed to hear how many times Jeremiah 17:9 popped up in peoples conversations. You have probably heard it a million times before as well, “"The heart is deceitful above all things, And desperately wicked; Who can know it?”. I just found it strange though that so many believers confess this even though scripture clearly states that under the new covenant we were given new hearts.
Eze 36:26 I will give you a new heart and put a new spirit within you; I will take the heart of stone out of your flesh and give you a heart of flesh.
Eze 36:27 I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them.
See also Jer 24:7, Eze 11:19 and 2 Co 3:1-3
For any believer to still hold to Jer 17:9 so tightly he would have to conclude that God gives to His children, who have been born again, a brand new but still desperately wicked and deceitful heart. If that’s true it seems like a pointless transaction doesn’t it?
The fact is, that God uses our new hearts (as well as scripture) as the vehicle to speak to us. The New Testament is full of verses indicating that we can trust our new hearts to guide us.
2Co 4:6 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.
There are many more, but for brevities sake I will just give the references
Rom 2:14-15, 10:10, Acts 23:1, 1 Cor 11:28-32, 2 Cor 4:6, 13:5-7
Paul would not have urged us to examine ourselves if something in us was not trustworthy, he would have pointed us to something like the bible instead. Of course, that is not a swipe at the bible, the 2 should always exist in perfect harmony, and if they are not, we are either being dishonest with ourselves or misunderstand something in scripture. The honest and humble Christian will know when he is acting against God, the Spirit will convict Him and is faithful in doing so to him who will listen.
Despite this trust, there is still the danger posed by the enemy as well as the flesh. Acts 5:3-5 makes it clear that we can still knowingly and willfully disobey the law within us and in so doing we can become hard hearted.
Rabbit hole to go down.
The old man needed the law because without it “every man did what was right in their own eyes”. Today we call it relativism and we all know where that road leads. Paul spends the first 8 chapters of Romans on this theme. It’s interesting that we are no longer under law yet how it is still pushed on people in some form today. As long as Christians are told that they cannot trust their heart, they will be forced to rely on the old system of do’s and do nots.