John Calvin Commentary Matthew 16:15

"He saith unto them, But who say ye that I am?" — Matthew 16:15 (ASV)

But who do you say that I am? Here Christ distinguishes His disciples from the rest of the crowd, to make it more fully evident that, whatever differences may exist among others, we at least should not be led aside from the unity of faith. Those who honestly submit to Christ, and do not attempt to mix with the Gospel any inventions of their own brain, will never lack the true light. But here the greatest vigilance is necessary, so that, even though the whole world may be carried away by its own inventions, believers may continually adhere to Christ.

As Satan could not rob the Jews of the conviction they derived from the Law and the Prophets that Christ would come, he changed Him into various shapes and, as it were, cut Him in pieces. His next scheme was to bring forward many pretended Christs, so that they might lose sight of the true Redeemer. By similar contrivances, he continued afterwards either to tear Christ in pieces or to exhibit Him under a false character.

Among the confused and discordant voices of the world, let this voice of Christ perpetually sound in our ears, which calls us away from unsettled and wavering men, so that we may not follow the multitude, and so that our faith may not be tossed about among the billows of contending opinions.