A Perfect Heart
There are not very many things in this fallen world that we would consider to be perfect. Maybe a short list of God’s beautiful creation, and a newborn baby. But, in Deuteronomy 18:10 God instructed the Israelites to walk perfectly before Him. He meant that they should keep their hearts pure by worshipping Him only. In doing so, He would see to it that they had everything they needed to live.
The Lord still expects us to live perfectly before Him. That's why in Psalm 138:8 the Psalmist, David wrote:
The LORD will perfect that which concerneth me: thy mercy, O LORD, endureth for ever: forsake not the works of thine own hands. Speaking of his hands working perfection in himself.
Psalm 57:2 I will cry unto God most high; unto God that performeth (completes, perfects) all things for me. He can make a perfect heart.