The New Testament writers also speak of the heart.  Those with hardened hearts, who do not hear and do not see, who refuse to turn to God.. bring grief and sorrow to our hearts and to His Heart also.
He calls us to open our hearts, to allow His Word to be planted in good soil, in an honest and good heart.

Do we have a "hardened heart"?  Is it dull or are we close-minded?  Is our heart far from Him?
What do we do?

We desire pure hearts, circumcised, willing, opened to Him. Barnabas preached to the new believers in Antioch, encouraging them all with "resolute heart to remain true to the Lord".  We begin with a resolute heart - the Greek work here is prothesis - a setting forth, from prothumia - forwardness of mind; readiness of mind; a ready and willing mind.   To have the kind of heart that David had - to be men and women "after" God's heart, willing to do what He wills - we need to turn our hearts - our minds, thoughts, and intentions to Him.

We believe first in our hearts and confess with our mouths that Jesus as Lord.  We trust in Him to remove the veil that has covered our hearts. We let His Word, which is living and active, sharper than any two-edged sword - to pierce our hearts - to judge the thoughts and intentions of our hearts.
We draw near "with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water" ( Hebrews 10:22)

God is greater than our heart, John writes. ( I John 3:20)  Our Lord knows all things.  He will lead us to His Truth. He will give us sincere hearts.  He will write on our hearts and strengthen our hearts with grace.  When we treasure His Word in our hearts, out of that heart will come what is good!

How wonderful is Your Word, Your living and active Word.  Fill our hearts O Lord, with the riches of Your Grace through Your Spirit.  Create in us clean hearts. Resolute hearts. Glad hearts, full of Your peace and the desire to do Your will. Always, sincerely, and earnestly.  We ask this in the Name of our Lord, Jesus Christ, Amen