I've heard that quote of St. Jerome's many times. But I wanted to know its context. It comes from his introduction to the book of the Prophet Isaiah. It's written in Latin, of course, but it didn't take me long to find a decent English translation of it.
[I obey] the precepts of Christ who says "examine the Scriptures" (John 5:39) and "seek and you will find." (Matt 7:7) Let me not hear with the Jews: "you are wrong because you do not know scriptures nor the power of God." (Matt. 22:29) For if, according to the apostle Paul, Christ is "the power of God and the wisdom of God" (1 Cor. 1:24) and who does not know Scripture does not know the power or the wisdom of God, then ignorance of Scripture is ignorance of Christ.