The Inter-Testamental period, approximately 400 years between the time of Malachi and Matthew, was a time of intense political and intellectual fermentation.
The thesis of Chronicles seems to be that when God's people seek Him in repentance and humility, God comes to their aid; if not, they fail.
The Jews turned a Babylonian myth of Lilith into a fabrication about a woman before Eve. Some translations suggest Israel sacrificed to a demon named Azazel.
The books of Zechariah and Malachi create a bridge to the New Testament and the coming of the Son of Man.
Righteousness consists of applying the Law's letter and/or intent. Sin constitutes a failure of living up to the standards of what God defines as right.
God is establishing a spiritual kingdom, with Christ as King, installed at the seventh trump when He will unleash the power of His Kingdom against the world.
The Sermon on the Mount is as vitally important today as when Christ preached it. It contains the way we are to live as God's representatives on this earth.