Galatians 5:9

On verses 8 to 12

This persuasion of yours is not from him who calleth you; is not from God: and I hope you will be shortly again of no other mind than what I taught you. (Witham)

This was a Jewish proverb, and alluded to the time of the Pasch, when it was not permitted to eat of any but unleavened bread; during which time the least leaven made the whole mass unclean to a Jew....Some Greek copies read, mikra zume olon to phurama zumoi, when the sense will be, "a little leaven causes the whole mass to rise." (Calmet)

Hence the introduction of any, however small, share of the ceremonial and Jewish rites, will greatly disfigure the purity and simplicity of the Christian institute.

As for me, my adversaries misrepresent me, when they say I preach circumcision; which if I did, I should not be persecuted as I am by the Jews. I never preach it necessary for Gentiles converted, though I have not condemned the use of it in the Jewish converts, provided they do not oblige other converts to it.

The scandal of the cross is therefore made void. The sense is, according to St. Jerome, that the Jews' greatest objection against St. Paul used to be, because he preached that circumcision and the law of Moses need not be observed: another objection against him was, that he preached Jesus, who was crucified on an infamous cross, to be their great Messias. He reasons then in this manner, that if the Jews think he again preacheth the necessity of circumcision and the precepts of the old law, they will no longer be offended that he preacheth Christ crucified, because they were not so much offended with the latter as with the first. Thus also St. Chrysostom on this verse. Others expound it thus: If I preach circumcision and the ceremonies of the law, therefore according to my doctrine, the cross of Christ, and justification by the merits of Christ crucified, is abolished, because justification is still to be sought for by the works of the law.