Today we start with the academic question – in Galatians 3:19

 19What, then, was the purpose of the law? 

A promise had been given to Abraham back in Genesis. But the law came later in Exodus.

The answer to the question is: It was added because of transgressions until the Seed to whom the promise referred had come. 

Where there is no law, there is no sin. It's the presence of the law that makes us conscious of our sin and need for God's grace. Galatians 3:19 Why, then, was the law given? It was added for the sake of transgressions until the Seed to whom the promise was made would come. The law was put into effect through angels by means of a mediator. 20 Now a mediator is not just for one person alone, but God is one. 21 Is the law therefore contrary to God’s promises? Absolutely not! For if the law had been granted with the ability to give life, then righteousness would certainly be on the basis of the law. 22 But the Scripture imprisoned everything under sin’s power, so that the promise might be given on the basis of faith in Jesus Christ to those who believe. 23 Before this faith came, we were confined under the law, imprisoned until the coming faith was revealed.