'Fall Away' in the Bible

then the priest shall cause the woman to swear with the oath of cursing, and the priest shall say to the woman, LORD make thee a curse and an oath among thy people when LORD makes thy thigh to fall away, and thy body to swell.

And this water that causes the curse shall go into thy bowels, and make thy body to swell, and thy thigh to fall away. And the woman shall say, Amen, Amen.

From Manasseh also there fell away some to David when he came with the Philistines against Saul to battle. But they did not help them, for the lords of the Philistines sent him away upon advisement, saying, He will fall away to his