How are the Mosaic law covenant and the Davidic royal covenant related to the Abrahamic covenant?
The Mosaic law covenant and the Davidic royal covenant are presented as coming under the Abrahamic covenant. God made the covenant of law with Moses and the covenant of a royal family with David, but they are all wrapped up in the Abrahamic covenant. Thus the Abrahamic covenant encompasses both later covenants.
Les explains that the covenant with them goes back to Abraham. He notes that there were other covenants that came under the Abrahamic covenant: God made the covenant of law with Moses and He made the covenant of a royal family with David. Yet all these are wrapped up in that Abrahamic covenant. The Abrahamic covenant is thus the covenant that contains the Mosaic and Davidic covenants.