Which is just a way of saying that the concrete revelation of God and his will at Sinai is normative for the whole of the Old Testament.
John's gospel is very interested in revelation, and undertakes to ask and answer afresh the question of how we come to know about God. Hence programmatic statements like "No one has ever seen God; the only God, who is at the Father's side, he has made him known" (1:18). The answer to the question is that we know God through his incarnate Son. This point is hammered home throughout the gospel account through Jesus' claims to unique knowledge of heaven (3:11-13), unique knowledge of the Father (8:55) and most stunningly unique and comprehensive revelation of the Father (8:19 amongst many others).
Perhaps the most astonishing statement in this regard is found in Jesus' last discussion with his disciples on the night he was betrayed. Ponder John 14:7 - "If you had known me, you would have known my Father also. From now on you do know him and have seen him". The ensuing conversation with Philip makes Jesus' point abundantly clear: if you want to see God, you must look at me, and what is more you must not look elsewhere (as Philip wants to).
The NT presents with a similarly concrete revelation of God, which sums up and supercedes everything in the OT. (I won't try to defend the latter clause here and now - maybe some other time). Just as OT Israel couldn't be imaginitive about God, the disciples of Jesus cannot go groping around their own thoughts or the world around them to find the divine. They need revelation, and revelation stands right in front of them in Jesus - in a very solid, fleshly form.
To be continued...