You are conflating justification and sanctification. One who is justified possesses the Holy Spirit. The Holy Spirit is the eternal Seal of redemption placed on His child eternally. If one possesses the Holy Spirit, there is no possibility that person could EVER go to hell. http://wayofthetabernacle.com/between_belief_salvation.htm
The Son is the Word of God. The Word of God defined His Word in Lk 24 as Moses, the Prophets and the Psalms. There was no New Testament, so to believe as those believed when He was here in the flesh, we must believe all that He spoke prior which was no different than what He spoke in the flesh. This is called being 'one' and since God does not change, neither does His Word, the same yesterday, today and forever.
Amo 3:7 Surely the Lord GOD does nothing, Unless He reveals His secret to His servants the prophets.
There is not one prophecy about a Messiah who comes to do it all for us so we no longer have to obey the commands. NONE!!! There is 'ONE' God, the is 'ONE' Word of God and that ONE Word is for all for all times. Ecc 12:13-14 - the duty of ALL MANKIND! Fear God and obey His commands.
The one who trusts in the Word of God, does the Word of God. The one who doesn't trust in the Word of God does not obey the Word of God. It is really very simple as our God is not a complicated God and neither is He the author of confusion. Lawlessness begets confusion, lawfulness begets harmony and peace. Then there is also the "if, then" scenario. If we will, then He will .. 2 Chron 7:14 as well as the first time the gospel message was uttered, Ex 19:5-6, Heb 4:2, 1Pet 2:9-10. The same gospel message then & now. Acts 7:37-39