Your confused brother as the same Old Testament law is the same law in the New Testament that gives us the knowledge of what sin is when broken *ROMANS 3:20; 1 JOHN 3:4; ROMANS 7:7 and leads us to Chrsit that we might be forgiven through faith *GALATIANS 3:22-25. If you have no law you have no knowledge of what sin is. If you do not know what sin is you have do not know you are a sinner in need of a Saviour. If you have no Saviour you have no salvation. If you have no salvation you are lost because you are still in your sins.
What do you think these scriptures mean?
MATTHEW 9:12-13 [12], But when Jesus heard that, he said to them,
They that be whole need not a physician, but they that are sick. [13],
But go you and learn what that means, I will have mercy, and not sacrifice: for
I am not come to call the righteous, but sinners to repentance.
If you have no law how do you know what sin is?
1 JOHN 3:4 [4], Whoever commits sin transgresses also the law: for
sin is the transgression of the law.
Read the scriptures in the OP. Everything we have in the NEW Testament comes from the OLD Testament scriptures. In the days of Jesus and the disciples the OLD Testament was their bible. Together both the OLD and NEW Testament scriptures make up the two great witnesses of the Word of God.
The Greek Word used for IF is the conditional particle of choice or to choose applied by free ...
“
IF” (Greek) *G1437; אםἐάν; ean;
a conditional particle; in case that, provided, etc.; often used in connection with other particles to denote indefiniteness or uncertainty : - before, but, except, (and) if, (if) so, (what-, whither-) soever, though, when (-soever), whether (or), to whom, [who-] so (-ever)., See G3361.
God's forgiveness is conditional...
I
JOHN 1:9 [9],
IF (conditional if we choose to; free will)
we confess our sins, he is faithful and righteous to forgive us our sins, and to cleanse us from all unrighteousness.
MATTHEW 6:14-15 [14], For
IF (conditional if we choose to; free will)
you forgive men their trespasses, your heavenly Father will also forgive you: [15], But
IF (conditional)
you forgive not men their trespasses, neither will your Father forgive your trespasses.
Being a disciple we must follow what Jesus says...
MATTHEW 16:24 Then said Jesus to his disciples,
IF (conditional if we choose to; free will) any man will come after me,
let him deny himself, and take up his cross, and follow me.
Conditons for inheriting eternal life...
MATTHEW 19:16-19 [16], And, behold, one came and said to him,
Good Master, what good thing shall I DO, that I may have eternal life? [17], And he said to him, Why call you me good? there is none good but one, that is, God: but
IF (conditional if we choose to; free will) you will enter into life, keep the commandments. [18], He said to him, Which? Jesus said, You shall do no murder, You shall not commit adultery, You shall not steal, You shall not bear false witness, [19], Honor your father and your mother: and, You shall love your neighbor as yourself.
JOHN 6:51 I am the living bread which came down from heaven:
IF (conditional if we choose to; free will)
any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
To many more in the OP to list here...
I choose to believe God's Word. How about you?