New Revised Standard Version
Why not? Because they did not strive for it on the basis of faith, but as if it were based on works. They have stumbled over the stumbling stone,

New American Bible
Why not? Because they did it not by faith, but as if it could be done by works. They stumbled over the stone that causes stumbling,

Douay-Rheims Bible
Why so? Because they sought it not by faith, but as it were of works. For they stumbled at the stumblingstone.

Why so? Because they sought it not by faith, but as it were of works. For they stumbled at the stumblingstone.

Because.

Romans 4:16 Therefore is it of faith, that according to grace the promise might be firm to all the seed: not to that only which is of the law, but to that also which is of the faith of Abraham, who is the father of us all,

Romans 10:3 For they, not knowing the justice of God and seeking to establish their own, have not submitted themselves to the justice of God.

Matthew 19:16-20 And behold one came and said to him: Good master, what good shall I do that I may have life everlasting? . . .

John 6:27-29 Labour not for the meat which perisheth, but for that which endureth unto life everlasting, which the Son of man will give you. For him hath God, the Father, sealed. . . .

Acts 16:30-34 And bringing them out, he said: Masters, what must I do, that I may be saved? . . .

1 John 5:9-12 If we receive the testimony of men, the testimony of God is greater. For this is the testimony of God, which is greater, because he hath testified of his Son. . . .

they stumbled.

Romans 11:11 I say then: Have they so stumbled, that they should fall? God forbid! But by their offence salvation is come to the Gentiles, that they may be emulous of them.

Matthew 13:57 And they were scandalized in his regard. But Jesus said to them: A prophet is not without honour, save in his own country, and in his own house.

Luke 2:34 And Simeon blessed them and said to Mary his mother: Behold this child is set for the fall and for the resurrection of many in Israel and for a sign which shall be contradicted.

Luke 7:23 And blessed is he whosoever shall not be scandalized in me.

1 Corinthians 1:23 But we preach Christ crucified: unto the Jews indeed a stumblingblock, and unto the Gentiles foolishness: