False teachers and their bad doctrine

The Lord repeatedly insists on the danger of false prophets, who will lead many to their spiritual ruin1. In the Old Testament reference is also made to these evil shepherds who wreak havoc among God's people. Thus, the Prophet Jeremiah denounces the impiety of those who prophesy by Baal and mislead my people Israel, deceive them and tell them their own fantasies and not the words of Yahweh..., they lead my people astray with their lies and their boasts, when I have not sent them, nor have I given them any mission, nor have they done my people any good2. Soon they also appeared in the bosom of the Church. St. Paul calls them false brethren and false apostles3, and warns the early Christians to beware of them; St. Peter calls them false doctors4. In our days, too, teachers of error have proliferated; the sowing of bad seeds has been abundant, and they have been a cause of bewilderment and ruin to many.

In the Gospel of the Mass the Lord warns us: Beware of false prophets; they come in sheep's clothing, but inwardly they are ravening wolves. They cause great harm to souls, for those who come to them in search of light find darkness, they seek strength and find uncertainty and weakness. The Lord Himself tells us that both the true and the false envoys of God will be known by their fruits; the preachers of false reforms and doctrines will bring nothing but the disunion of the fruitful trunk of the Church and the disturbance and perdition of souls: by their fruits you will know them, Jesus tells us. Are grapes harvested from brambles or figs from thistles? Healthy trees bear good fruit; damaged trees bear bad fruit. A healthy tree cannot bear bad fruit, nor can a damaged tree bear good fruit. In this passage of the Gospel the Lord warns us to be vigilant and prudent with false doctors and with their deceitful doctrines, for it will not always be easy to distinguish them, since bad doctrine often presents itself in the guise of goodness and goodness.