“For if someone comes and proclaims another Jesus than the one we proclaimed …” (v4). Paul was very “jealous” for the true gospel (v2), and he was concerned that the Corinthians were being led astray (v3). So-called “super apostles” were showing off with charismatic preaching (but changing the message) and enriching themselves; Paul, on the other hand, was humble in person and worked hard to not to financially burden the believers (v7-9). Paul said that these “false apostles” were doing Satan’s work (v13-15).
To cultivate “sincere and pure devotion to Christ” (v3) and avoid false teaching, we must know Jesus as revealed in the Word and through the power of the Spirit.