The Christian churches in Judea, however, were not totally ignorant of Paul; they had heard what others were saying about him. The others are probably to be understood primarily as members of churches which had been the special targets of Paul’s persecuting activities.
The faith should not be understood as a body of Christian doctrine, but either as a synonym for the good news or as a term referring to the Christian movement in general (compare verse 13).
The word for “tried to destroy” is the same verb as in verse 13. For a number of languages there are complications involved in the expression is now preaching the faith that he once tried to destroy, since “faith” cannot be the direct object of the customary equivalent expressions for “preaching” and “destroy.” One can often speak about “preaching the good news,” but what Paul set out to destroy was not the good news but rather those who believed the good news or the Christian movement as such. If one renders faith as “trust,” then this must obviously refer to “trust in Christ” or “believing in Christ.” One may therefore render is now preaching the faith as “is now telling people how they should trust in Christ.” The final clause that he once tried to destroy may then be rendered as “before he was trying to destroy those who trusted in Christ,” or “whereas before that he had been trying to stop people believing in Christ.”
Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Galatians. (UBS Handbook Series). New York: UBS, 1976. For this and other handbooks for translators see here .