Understanding Levitical law

  There is some confusion on how Levitical or Mosiac law relates to Christians. They are often used to accuse Christians of cherry picking the Bible, however such accusations are made out of ignorance. There are 613 Levitical laws that fell into one of three categories: civil, ceremonial, and moral. Civil related to the affairs of government. Ceremonial related to the affairs of the priest, sacrificial laws, dietary laws, cleansing, etc. Moral laws related to sexual sins, stealing, murder, the ten commandments, and so on.

The civil and ceremonial laws were specifically intended for Israel at that time, under the Old Covenant. Some may wonder here why God cared about what His people ate or why sanitation was important. However, these laws did have practical applications. The ceremonial laws taught proper hygiene. In fact, during the middle ages as the black plague was sweeping across Europe, Jews were often less affected specially because their religious faith promoted better hygiene and sanitation. As for the dietary laws, most of what God forbade them to eat was actually unhealthy. The Israelites at this time, of course, had no concept of nutrition. However, God did and it is perfectly reasonable that he would want His chosen people to remain healthy.

Christians have never the Levitical laws, especially the the civil and ceremonial laws. However, we do still observe the moral laws, which is universally binding and still applicable today. If something was morally wrong in the Old Testament, it is still morally wrong in the New Testament. The difference is now we live in an age of grace, and breaking those laws don't come with an automatic death sentence as they did in the Old Testament. However, the wages of sin are still death, that is eternal separation from God.
 
The Levitcal laws were ultimately meant to teach right from wrong. It's been said the laws were given to show the Isralite people that they needed a Messiah, because it was impossible to keep all the laws perfectly. As such, every year an animal sacrifice was needed to atone for the sins of the nation. Jesus being sinless and blameless became the perfect sacrifice and the Levitcal laws became unnecessary.

Understanding Psalm 137:9

Psa 137:8 Daughter Babylon, doomed to destruction, happy is the one who repays you according to what you have done to us.
Psa 137:9 Happy is the one who seizes your infants and dashes them against the rocks.

Does Psalm 137:9 support infanticide? Not hardly, context is everything. First a little back story. Psalm 137 takes place during the Jewish exile in Babylon (modern day Iraq). The Babylonians had come against Judah and besieged Jerusalem for eighteen months. The account is detailed in the Book of Lamentations. The siege was so serve that the people were starving to death. Children and infants were dying in the streets (lam 2:11-12, 19, 4:4), and mothers were boiling their babies for food (Lam 2:20, 4:10). The city eventually fell and the Jews were taken captive to Babylon.

Psalm 137 opens with the Jews lamenting what had happened in Jerusalem. They remembered what the Babylonians did to them and their children and wanted vengeance. They also remembered what the prophet Isaiah had prophesied nearly two centuries earlier about the fate of Babylon:

Isa 13:16 Their infants will be dashed to pieces before their eyes; their houses will be looted and their wives violated.
Isa 13:17  See, I will stir up against them the Medes, who do not care for silver and have no delight in gold.
Isa 13:18 Their bows will strike down the young men; they will have no mercy on infants, nor will they look with compassion on children.
Isa 13:19 Babylon, the jewel of kingdoms, the pride and glory of the Babylonians,will be overthrown by God like Sodom and Gomorrah.

The Jews were rejoicing that the Babylonians would be repaid for what was done to them and their children, but retribution wouldn't come from the Jews but from the Medes. This is exactly what happened. Babylon was captured in one night by the Medes and Persians under Cyrus the Great. Several years later there was a rebellion that was put down by King Darius and the rebels impaled in the city. In 482 B.C. Babylon rebelled again and was destroyed by King Xerxes, fulfilling the words of Isaiah. So Psalm 137:9 is a nod to Isaiah 13:16-19. It doesn't condone infanticide, merely iterates what would happen to the Babylonians by the Medes and Persians.