John Calvin Commentary Matthew 16:12

"Then understood they that he bade them not beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees." — Matthew 16:12 (ASV)

Then they understood. The word leaven is very evidently used by Christ as contrasted with the pure and uncorrupted word of God.

In a former passage (Matthew 13:33), Christ had used the word in a good sense, when he said that the Gospel resembled leaven;⁴³⁴ but for the most part, this word is employed in Scripture to denote some foreign substance by which the native purity of anything is impaired.

In this passage, the naked truth of God and the inventions which men contrive from their own minds are unquestionably the two things that are contrasted.

The sophist must not hope to escape by saying that this should not be understood as applicable to every kind of doctrine, for it will be impossible to find any doctrine, except what has come from God, that deserves the name of pure and unleavened.

Hence it follows that leaven is the name given to every foreign admixture, as Paul also tells us that faith is rendered spurious as soon as we are drawn aside from the simplicity of Christ (2 Corinthians 11:3).

It must now be apparent who the persons are whose doctrine our Lord charges us to beware of.

The ordinary government of the Church was at that time in the hands of the scribes and priests, among whom the Pharisees held the highest rank.

As Christ expressly charges his followers to beware of their doctrine, it follows that all who mingle their own inventions with the word of God, or who advance anything that does not belong to it, must be rejected, however honorable their rank may be, or whatever proud titles they may wear.

Accursed and rebellious, therefore, is the obedience of those who voluntarily submit to the inventions and laws of the Pope.

⁴³⁴ See page 127 of this volume. of this volume.