On first reading, the passage above suggests the magnitude and mystery of God’s will. It appears that we are not to question God or the workings of God. For who are we to answer back, to back-talk to God? And this is true.
However, this reasoning by Paul goes beyond a general comment about humanity before God, for what the apostle is suggesting is in response to a very specific, real-life situation. Paul is speaking here about the place of Gentiles in the kingdom of God as over against Israel. The complaint, evidently, was from Jews who couldn’t understand why God would save Gentiles (non-Jews) without requiring that they become children of Israel first. Paul reasons that God can save whom He will and that, indeed, Israel has been/is being judged for pursing righteousness through works rather than faith. Paul says, “They [Israel] have stumbled over the stumbling stone, as it is written, ‘Behold, I am laying in Zion a stone that will make men stumble, a rock that will make them fall; and he who believes in him will not be put to shame.” (vss. 32-33)
The stumbling block is faith in Jesus Christ, and men will stumble over it because humans will always prefer to have salvation dependent upon us, rather than upon a Savior, Christ the Lord. Humans believe that we ought to be able to earn our way into heaven through our own goodness, good works and abilities; so that we can know we’ve got salvation all wrapped up, thank you very much! Another chore in this life taken care of and checked off our list of things to do. Salvation? Check! Got ‘er done!
No wonder, then, that people stumble over the stumbling stone—the truth that we cannot save ourselves by our own reason or strength, but that salvation is wholly, completely, totally the work and gift of God, through Jesus Christ, by the power of the Holy Spirit.
Almighty God, you are the potter—we are the clay. Mold us, shape us, fill us with faith in Jesus Christ, that we may not stumble over the stumbling stone; in Jesus’ name we pray. Amen.
Taken from Wendel, David, From Ashes to Easter, Ashes Lenten Devotional Booklet, North American Lutheran Church.