Charles Ellicott Commentary 1 Corinthians 8:12

"And thus, sinning against the brethren, and wounding their conscience when it is weak, ye sin against Christ." — 1 Corinthians 8:12 (ASV)

When ye sin so.—When you sin in this way—and he explains further what the sin is: “Striking a blow upon their weak consciences”—you sin against Christ. You wound a member of that body which is His. (See Matthew 25:40.)