Romans 4

Paul used Abraham as an example to illustrate that we are saved through our belief in God and not by our works. He quoted scripture that said Abraham was considered righteous because he believed. He noted that this was said of Abraham before he was circumcised. Therefore, the act of circumcision was not the source of his salvation. It is the same for each of us. We are brought into the same promise given to Abraham not because of how well we keep God's law, but by believing in Him, accepting Him, and following Him.

How good do you have to be to get into heaven? Where is the pass/fail line on God's measuring stick? If there were one, it would be at the 100% mark - perfection. Only one man has lived a perfect life and His name was Jesus. We can't possibly hope to hit the mark of perfection, so God made a way for us to be considered righteous through belief in Him. Apart from that, there is no salvation. We can perform all the religious ceremonies we want, donate all our money to the church or to the poor, memorize scripture, and any number of other things in order to please God, but without taking the first step of believing in him and trusting in Him, it doesn't amount to anything in His eyes.