Well, wait a minute, I am now thinking if God's new Convenant was to write his commandments in our hearts then why would we still not be obligated to obey "his" commandments?
You're thinking God literally wrote the 10 commandments on your heart?
It's more like that God gives the holy Spirit then if you listen to the Spirit then God can command you directly.
The Law of Moses was made for those who didn't have the holy Spirit yet. I like to use the analogy of a regent that rules the kingdom until the king comes of age. But once the king is on his throne then the work of the regent is finished.
If Moses is the regent and Jesus is the King. When the King is enthroned in your heart then the work of the regent is finished.
So before Jesus is enthroned in your heart; then you went to Moses' seat. Which is the regent and you obeyed God indirectly through the rules of the Law of Moses.
Matthew 23:2-3
Saying The scribes and the Pharisees sit
in Moses' seat: All therefore whatsoever they bid you observe, that observe and do; but do not ye after their works: for they say, and do not.
But when Jesus is enthroned in your heart then the Law proceeds from Him directly. That is you obey the Spirit which is the "River of Life" that flows from the throne.
Hebrews 4:14-16
Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin. Let us therefore come boldly
unto the throne of grace, that we may obtain mercy, and find grace to help in time of need.
So the leading of the Spirit makes the Law of Moses superfluous. The Law of Moses served it's purpose and now if you're born of the Spirit; you're coming to the throne of grace. You have access into the holiest of holies without restriction.
Galatians 5:18
But if ye be led of the Spirit, ye are not under the law.
Revelation 22:1
And he shewed me a pure river of water of life, clear as crystal,
proceeding out of the throne of God and of the Lamb.
Isaiah 51:4
Hearken unto me, my people; and give ear unto me, O my nation:
for a law shall proceed from me, and I will make my judgment to rest for a light of the people.