What Is Sin? (A Rabbinical Perspective)

Psalm 25
Of David.
1 In you, Lord my God,
I put my trust.
2 I trust in you;
do not let me be put to shame,
nor let my enemies triumph over me.
3 No one who hopes in you
will ever be put to shame,
but shame will come on those
who are treacherous without cause.
4 Show me your ways, Lord,
teach me your paths.
5 Guide me in your truth and teach me,
for you are God my Savior,
and my hope is in you all day long.
6 Remember, Lord, your great mercy and love,
for they are from of old.
7 Do not remember the sins of my youth
and my rebellious ways;
according to your love remember me,
for you, Lord, are good.
8 Good and upright is the Lord;
therefore he instructs sinners in his ways.
9 He guides the humble in what is right
and teaches them his way.
10 All the ways of the Lord are loving and faithful
toward those who keep the demands of his covenant.
11 For the sake of your name, Lord,
forgive my iniquity, though it is great.
12 Who, then, are those who fear the Lord?
He will instruct them in the ways they should choose.[b]
13 They will spend their days in prosperity,
and their descendants will inherit the land.
14 The Lord confides in those who fear him;
he makes his covenant known to them.
15 My eyes are ever on the Lord,
for only he will release my feet from the snare.
16 Turn to me and be gracious to me,
for I am lonely and afflicted.
17 Relieve the troubles of my heart
and free me from my anguish.
18 Look on my affliction and my distress
and take away all my sins.
19 See how numerous are my enemies
and how fiercely they hate me!
20 Guard my life and rescue me;
do not let me be put to shame,
for I take refuge in you.
21 May integrity and uprightness protect me,
because my hope, Lord,[c] is in you.
22 Deliver Israel, O God,
from all their troubles!

Like almost everything else, it depends on who you ask.
The Midrash (Yalkut Shimoni on Psalms 25) describes a sort of "panel discussion" in which this question is posed to four different authorities — Wisdom, Prophecy, Torah and God — each of whom gives a different definition of sin.
According to Wisdom sin is a harmful deed. According to Prophecy it is death. Torah sees it as folly. And God sees it as an opportunity.
The philosophical view of sin is that it is a bad idea, like walking barefoot in the snow or eating too many fatty foods. If you do bad things, bad things will happen to you.
Does this mean that Someone sits up there, tabulating sins and dispensing punishments? Well, yes, though it is not as simplistic as a vengeful God getting even with His little earth creatures for daring to defy His instructions.
Is frostbite God's punishment for that barefooted walk in the snow? Is heart disease God's revenge for a high-cholesterol diet? Ultimately it is if you accept that everything that happens, happens because God wants it to happen. But what it means is that God has established certain "laws of nature" that describe the patterns of His actions upon our existence. There are physical laws of nature — the ones that scientists measure and hypothesize. There are also spiritual laws of nature, which dictate that spiritually beneficial deeds bring spiritual benefit and spiritually detrimental deeds cause spiritual harm. And since our physical existence derives from and mirrors the spiritual reality, a person's spiritual and moral behaviour ultimately affects his physical life as well.
Thus King Solomon states in the book of Proverbs: "Evil pursues iniquity."
"Prophecy" takes this a step further. Sin is not only a harmful deed — it is the ultimately harmful deed. Prophecy (which represents the apogee of man's endeavour to commune with God) defines "life" as a connection with God.
Sin—man's turning away from God—is a disruption of this connection. Hence, sin is death.
Torah agrees that sin is a harmful deed. It also agrees that it's a disruption of the flow of life from Creator to creation.
Indeed, the Torah is the source of both Wisdom's perspective and Prophesy's perspective on sin. But Torah also goes beyond them both in recognizing that the soul of man would never willingly and consciously do such a stupid thing.
Sin, says Torah, is an act of folly. The soul loses its head, and in a moment of irrationality and cognitive confusion does something that is contrary to its true desire. So sin can be transcended when the soul recognizes and acknowledges the folly of its transgressions and reasserts its true will. Then the true self of the soul comes to light, revealing that the sin was in fact committed only by the soul's most external, malleable self, while its inner self was never involved in the first place.
And what does God say? God, of course, invented the laws of nature (both physical and spiritual) and the Wisdom that recognizes how they operate. G‑d is the source of life, and it is He who decreed that it should flow to the human soul via a channel constructed (or disrupted) by the deeds of man. And G‑d gave us the Torah and its formulae for spiritual sanity, self-discovery and transcendence. So God is the source of the first three perspectives on sin.
But there is a fourth perspective that is God's alone: sin as the opportunity for "return" (teshuvah).
Teshuvah is a process that, in its ultimate form, empowers us to not only transcend our failings but to also redeem them: to literally travel back in time and redefine the essential nature of a past deed, transforming it from evil to good.
To achieve this, we first have to experience the act of transgression as a negative thing. We have to agonize over the utter devastation it has wrecked on our souls. We have to recognize, disavow and renounce its folly. Only then can we go back and change what we did.

How do we go back? We repent of our old ways of doing things and embrace the gift of salvation that has been freely offered to us through the Lord Jesus Christ.
Once you come to Christ, you receive eternal life and you have the gift of salvation imputed into you. This gift affords you the opportunity to assess your past and make peace with the past by ditching darkness for the light and embracing the new life in Christ while dumping the old life and all its entrapments.
The Christian is absolutely saved from the shame of sin, he or she left the reality of sin for the glory that is in Christ Jesus once and for all by embracing the life of God through the gift of salvation.

-GSW-