58 Grk “Why? Because not by faith but as though by works.” The verb (“they pursued [it]”) is to be supplied from the preceding verse for the sake of English style; yet a certain literary power is seen in Paul’s laconic style.
59 Most , especially the later ones (א2 D Ψ 33 𝔐 sy), read νόμου (nomou, “of the law”) here, echoing Paul’s usage in Rom 3:20, 28 and elsewhere. The qualifying phrase is lacking in א* A B F G 6 629 630 1739 1881 lat co. The longer reading thus is weaker externally and internally, being motivated apparently by a need to clarify. Grk “but as by works.”
60 Grk “the stone of stumbling.”

In other versions

ESVEnglish Standard Version

Why? Because they did not pursue it by faith, but as if it were based on works. They have stumbled over the stumbling stone,

NIVNew International Version (2011)

Why not? Because they pursued it not by faith but as if it were by works. They stumbled over the stumbling stone.

CSBChristian Standard Bible

Why is that? Because they did not pursue it by faith, but as if it were by works. They stumbled over the stumbling stone.

NLTNew Living Translation

Why not? Because they were trying to get right with God by keeping the law instead of by trusting in him. They stumbled over the great rock in their path.

LEBThe Lexham English Bible

Why that? Because they did not pursue it by faith, but as if by works. They stumbled over the stone that causes people to stumble,

KJV 1900King James Version

Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone;

Public Domain