Here's what salvation hinges on:
1. Belief on God.
2. Obedience to God.
We need both.
Now to your verses:
Romans 3:20
19 Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God;
20 because by the works of the Law no * flesh will be justified in His sight; for through the Law comes the knowledge of sin.
We are not saved by our good deeds.
Have stated this a couple of times now.
1 John 3:4
4 Everyone who practices sin also practices lawlessness; and sin is lawlessness.
Of course.
John learned this from Jesus, who stated:
Matthew 7:23
23 "And then I will declare to them, 'I never knew you; DEPART FROM ME, YOU WHO PRACTICE LAWLESSNESS.'
Jesus explains WHY He never knew them...
because they practiced lawlessness.
And if we read just a few verses down John states:
1 John 3:7-8
7 Little children, make sure no one deceives you; the one who practices righteousness is righteous, just as He is righteous;
8 the one who practices sin is of the devil; for the devil has sinned from the beginning. The Son of God appeared for this purpose, to destroy the works of the devil.
We are told by John to practice righteousness.
We are told that if we practice sin we are of the devil.
John tells us that Jesus appeared to destroy the works of the devil.......
that would be sin.
Sin is DISOBEDIENCE to God. The very difinition of sin.