Summary: When we believe in the God who raised Jesus our Lord from the dead, our faith also will be accounted as righteousness.
NOT THROUGH LAW
The Apostle Paul has already established that Abraham was not justified (made righteous) by works, otherwise he would have grounds of boasting - and who can boast before God? (Romans 4:2). Neither was Abraham justified by circumcision, since that rite was not introduced until AFTER the patriarch’s justification (Romans 4:11). It stands to reason that, if Abraham was not justified by works, then neither was he justified by the law (which had not yet been given - cf. Galatians 3:17).
In the Greek, the Apostle places the phrase “For not through law” emphatically, at the beginning of a sentence (Romans 4:13). The teaching throughout the Scripture is that Abraham, and his spiritual progeny, are justified (made righteous) by faith.
The argument continues that, if the inheritance belongs to those who supposedly keep the law, then faith has been emptied, and the promise has been rendered ineffective (Romans 4:14; cf. Galatians 3:18).
Which all brings us back to Abraham, and his spiritual seed (who are those who share his faith). If Abraham believed for the land (Genesis 13:15), and for the progeny (Genesis 15:5-6), it is also clear that he believed in God as the one who raises the dead, as he would later prove (Romans 4:17; cf. Hebrews 11:17-19).
So, where all human hope ended, Abraham “in hope believed” the promise of God (Romans 4:18).
We are told here that Abraham was not weak in faith, even when confronted with both the lifelessness of his own body, and the corresponding barrenness of Sarah’s womb (Romans 4:19).
It is not that Paul was unaware of the old couple’s attempt to ‘help God out’ by the introduction of Hagar into the equation (Genesis 16:2), but rather the Apostle is taking the God’s-eye view. When God looks upon those whom He has justified, HE DOES NOT COUNT OUR SINS AGAINST US (2 Corinthians 5:19).
The emphasis falls upon Abraham’s unwavering faith in relation to the promise of God, his lack of unbelief, and his being strengthened in faith, giving glory to God (Romans 4:20).
Now, says Paul, this was not written for Abraham alone, that it was accounted to him as righteousness (Romans 4:23). ‘Whatever things were written before, were written for our learning, that we through the patience and comfort of the Scriptures might have hope’ (Romans 15:4; cf. 1 Corinthians 10:11).
When we believe in the God who raised Jesus our Lord from the dead, our faith also will be accounted as righteousness (Romans 4:24).
For the Lord was delivered over to death because of our sins, and was raised with a view to our justification (Romans 4:25).
After all, ‘if Christ is not raised, we are yet in our sins’ (1 Corinthians 15:17)!