The "Law" on our hearts

I used to think that the phrase pertaining to the Law "written on our hearts" was a "new" covenant phenomenon. I have come to know that this is way of thinking is misleading and is not consistent with Scripture. In reading Deuteronomy, I've found it very clear that the "law" was always meant to be on our hearts. Yet so far I've only noted Deuteronomy I will continue looking through the rest of the Scripture to find more references. I am amazed to read many times that those who were saved by Yahweh's arm of salvation, were told through Moses to take to heart the instructions given to them. They were to "take care, and keep your soul diligently, lest you forget the things that your eyes have seen, and lest they depart from your heart all the days of your life. Make them known to your children and your children's children--" (Deut 4:9)

I'm planning to stickie note my Scriptures every time I read about Yahweh's special instructions for our hearts. I wonder if it will be mentioned more in the Old than the New. Hmm... just wondering.