The natural human reaction would be to admonish and discipline the weak, sinning brother. Paul, however, emphasizes the sin of the other brother, who has acted from knowledge
rather than from love. By putting a stumbling block
in his brother’s way (1 Corinthians 8:9), he has sinned not only against his brother, but ultimately against Christ himself.
12 En péchant de la sorte contre les frères, et en blessant leur conscience faible, vous péchez contre Christ.