Those who rely on doing what is right to establish their righteousness, will always have a shock.  Legalistic righteousness is a matter of knowing the law and being disciplined to fulfil the rules and regulations.  It is about always keeping the rules, all the time with no exceptions.  But nobody, except Jesus, can live a completely perfect life (Romans 3:23), and so every time they fail to do right, they invite the weight of the law to condemn them.

The Jews, who revered the written Law of God, could never be made righteous by the good they achieved - because they all failed to keep it perfectly (James 2:10-11).  So, their devotion to the law of God would only bring God's anger against them.  Paul was teaching the Jewish-background believers that they were not ‘in the right’ with God because they kept the Law of Moses.  Abraham, who they celebrated as their ‘father’, lived some 500 years before Moses and did not have that law.  Even the command to circumcise, which God gave to Abraham, came after Abraham was declared righteous because he believed God’s Word (Romans 4:9-11).

So Abraham, who lived before the law was given, simply believed what God had said to him.  What Abraham believed was a promise that his offspring would be the means of the world's blessing (Genesis 15:1-5).  Because of his faith, God credited righteousness to him (Genesis 15:6).  Even though he did not know that Jesus would be the key figure in that blessing, he believed as much as he knew.  Jesus confirmed that by saying to the religious leaders, “Your father Abraham rejoiced at the thought of seeing my day; he saw it and was glad.” (John 8:56).

The Bible is full of God's promises. We cannot be saved without believing in the promise that all who repent and believe in Jesus will not perish but have everlasting life (John 3:16).  But there are many more promises too.  We can never do enough to satisfy God's law, but we can keep on trusting His Word and receiving His grace.  Such faith does not aim to attract material wealth and possessions now, but treasure in heaven (Matthew 6:19-21).  Believing His promises will give us the confidence to look forward with hope, enabling us to persist despite our troubles (2 Timothy 1:12).  Our faith is not in our ability to get everything right, but in Jesus and His power to fulfil His promises.  He is able to do immeasurably more than all we ask or imagine (Ephesians 3:20).  Like Abraham, we can only begin by faith.  Like Abraham, we have to continue by faith (Hebrews 10:38).