Romans 4:2

But not before God— This appears to be the Apostle's answer to the Jew's objection (Romans 4:1.), and it implies that Abraham might have some sort of glorying, possibly such as the Apostle himself had, 1 Corinthians 9:15. 2 Corinthians 1:12; 2 Corinthians 10:13; 2 Corinthians 10:18; 2 Corinthians 11:16. The Apostle had glorying in his superior vouchsafements and labour, but only before men, and with respect to them; not before God, in regard to whom his language was, Not I, but the grace of God. Note farther, that before God hints, that the Apostle considers Abraham as standing in the court before God's tribunal, when the promise was given him. It perhaps would make this passage clearer, if the present verse ended with the word glory, and the third began with the clause before us. See Raphelius.