The history of the decree:[1]
As is often the case with rabbinical enactments or decrees, the historical circumstances surrounding their original institution are not always fully recorded or documented. Nevertheless, some Poskim[2] suggest that the decree to educate one’s children in Mitzvos dates back to the time of Shmuel HaNavi. Other Poskim[3] maintain that it was originally instituted by Moshe Rabbeinu for his own generation, serving as the initial enactment, and that it was only later extended and formally decreed on behalf of the entire Jewish people.
[1] Encyclopedia Talmudit ibid p. 162 footnote 9; See Toras Hakatan [Rubinovitch] Chapter 1:1
[2] Turei Even Chagiga 6a
[3] Haemek Davar Devarim 11a