St. Paul’s First Letter to the Corinthians 10:5-12
Brethren, God was not pleased with most of the fathers; for they were overthrown in the wilderness.
Now these things are warnings for us, not to desire evil as they did.
Do not be idolators as some of them were; as it is written, “The people sat down to eat and drink and rose up to dance.”
We must not indulge in immorality as some of them did, and twenty-three thousand fell in a single day.
We must not put Christ to the test, as some of them did and were destroyed by the Destroyer. Now these things happened to them as a warning, but they were written down for our instruction, upon whom the end of the ages has come. Therefore
let any one who thinks that he stands take heed lest he fall.
The Lord said to his disciples, “Take heed and beware of the leaven of the Pharisees and Sadducees.” And they discussed it among themselves, saying, “We brought no bread.” But Jesus, aware of this, said, “O men of little faith, why do you discuss among yourselves the fact that you have no bread? Do you not yet perceive?
Do you not remember the five loaves of the five thousand, and how many baskets you gathered?
Or the seven loaves of the four thousand, and how many baskets you gathered?
How is it that you fail to perceive that I did not speak about bread?
Beware of the leaven of the Pharisees and Sadducees.” Then they understood that he did not tell them to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees.