Political redistribution of wealth is a sin because it is the act of playing God in the lives of people. Political redistribution of wealth plays God by usurping God's role as Provider. Consider the following scriptures:
"The earth is the Lord's and its fullness, the world and those who dwell therein." Psalm 24:1.
"And you shall remember the Lord your God, for it is He who gives you power to get wealth, that He may establish His covenant which He swore to your fathers as it is this day." Deuteronomy 8:18.
"May the Lord give you increase more and more, you and your children. May you be blessed by the Lord, Who made heaven and earth." Psalm 115:14.
Any entity that actively engages in redistribution of wealth sets itself up as a false god. The consequences of this are deadly. Consider the story of Herod Agrippa I1 in Acts 12. This is the same Herod that killed James the brother of John and put Peter in jail. Herod became angry with the people of Tyre and Sidon who were dependent on his country for food. After he delivered an oral address to them, the people of Tyre and Sidon declared Herod to be a god. Herod did not give glory to God and because of this was eaten to death by worms.
It is a very dangerous thing for men to look to other men as provider rather than looking to God. God has a plan for everyone's life. When men find and walk in God's plan for their lives, they also find and experience God's provision for their lives.
"Therefore I say to you, do not worry about your life, what you will eat or what you will put on. Is not life more than food and the body more than clothing?…For after all these things the Gentiles seek. For your heavenly Father knows that you need all these things. But seek first the Kingdom of God and His righteousness and all these things shall be added to you." Matthew 6:25, 32, 33.
"I will lift up my eyes to the hills - whence comes my help? My help comes from the Lord Who made heaven and earth. He will not allow your foot to be moved; He who keeps you will not slumber. Behold, He who keeps Israel shall neither slumber nor sleep. The Lord is your keeper; the Lord is your shade at your right hand. The sun shall not strike you by day, nor the moon by night. The Lord shall preserve you from all evil. He shall preserve y our soul. The Lord shall preserve your going out and your coming in from this time forth, and even forevermore." Psalm 121.
1 Hayford, Jack W. ed. Spirit-Filled Life Bible. New King James Version. Nashville: Thomas Nelson Publishers, 1991, p. 1648.