There’s a surprising comment in Genesis 26, in which the LORD assures Isaac that he will bless him, “Because that Abraham obeyed my voice, and kept my charge, my commandments (mitzvot), my statutes (chuqot), and my laws (torot)” (26:5). This language is otherwise unprecedented in the patriarchal period, but it strikingly anticipates the LORD’s commands to Israel after the giving of the Law at Sinai: “If thou…wilt give ear to his commandments (mitzvot) and keep all his statutes (chuqot) (Exod 15:26); “And the LORD said unto Moses, How long refuse ye to keep my commandments (mitzvot) and my laws (torot)? (Exod 16:28). The three terms, in various combinations, are pervasive in the Torah as descriptions of what the LORD requires of Israel.
On its face, the verse might suggest the kind of revision that we find in the post-biblical Book of Jubilees, in which Abraham and the other patriarchs observe Passover, keep kosher, and generally seem to have a detailed knowledge of the Sinai covenant. This reading is a solution to the problem of apparent righteousness apart from the Law (the problem of Genesis, as Walter Moberly calls it, as “the OT of the OT”) — Jubilees seems to suggest that there is no such righteousness!
Is that an acceptable Christian interpretation of this verse? I’m not sure. I’d be happier with reading it as describing an obedience that’s analogical to the obedience required of Israel under the Law, an obedience which in Abraham’s, David’s, and our cases is fundamentally rooted in an attitude of love for and trust in the LORD.