The Mosaic covenant demanded obedience, even to the extent that it could be called a condition of the covenant. But that was true of the Abrahamic covenant as well. Genesis 17.9 is not some different category from anything we later read at Sinai or later:
And God said to Abraham, ‘As for you, you shall keep my covenant, you and your offspring after you throughout their generations.
And God later elaborated on this, saying of Abraham,
For I have chosen him, that he may command his children and his household after him to keep the way of the LORD by doing righteousness and justice, so that the LORD may bring to Abraham what he has promised him (Genesis 18.19, emphasis added).
There is not anything in the necessity of keeping the Mosaic Covenant and obeying God’s voice that is different in principle from what is involved in what the covenant required of Abraham.