The Law of Return appears in various verses of the Bible: "For whatsoever a man soweth, that shall he also reap" Galatians 6: 7, "For the wages of sin is death, but the gift of God is eternal life" Romans 6:23, " Who sows in the spirit will from the spirit reap eternal life "Galatians 6: 8," In the same way you judge others, you will be judge, and with the measure you use, it will be measure to you "Matthew 7: 2.
The Law of Return, "you reap what you  sow," is a law of balance and retribution. It is a law of retribution because is logical that we receive in the same way we gave, or to say the environment returns us the same that we give. It is a law of balance because tends to the correction of the error , punish the mistakes and reward the right actions.
We can express the concept of balance in another sense, from the analysis of the Beatitudes of the Gospel of Luke and Matthew.
The Beatitudes of Luke teach us about 4 Beatitudes Luke 6: 20-22, and 4 curses that constitute the false happiness, Luke 6: 24-26; the difference between the 4 blessings and the 4 curses of the Gospel of Luke is the Law of the Return.
Let's see the beatitudes in the Gospel of Matthew: Blessed are the merciful, for they will be shown mercy, Matthew 5:7. What the beatitude teach to us is that if we sow mercy we shall reap mercy. Another example: Blessed are the pure in heart because they shall see God. Purity of heart means integrity and seeing God means contemplation. In other words the return of integrity is contemplating God.
The Beatitudes are the practical expression of God's plan. All Beatitudes follow the same structure: (law of God) (Spiritual Gift) (law of retribution or balance) (associated blessing). 
What this structure tells us? The significance of this structure, which is telling us is that God established laws to govern the creation and these laws adminsitran his gifts, his perfections. And within these laws there is a law of cosmic balance that can be expressed as "you reap what you sow". The law of return as the law of balance returns curse for the sinner and blessings to the righteous.