Deuteronomy 32:46

⁴⁶ And he said unto them, Set your heart unto all the words which I testify unto you this day, which ye shall command your children to observe to do, [even] all the words of this law.

Days of old

The days of old (Psalms 77:5) signify states of the most ancient church, years of ancient times, and states of the ancient church.