The Pharisees and Sadducees came, and to test Jesus they asked him to show them a sign from heaven.
References for Matthew 16:1
He answered them, "When it is evening, you say, "It will be fair weather, for the sky is red.'
And in the morning, "It will be stormy today, for the sky is red and threatening.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times.
References for Matthew 16:3
An evil and adulterous generation asks for a sign, but no sign will be given to it except the sign of Jonah." Then he left them and went away.
When the disciples reached the other side, they had forgotten to bring any bread.
Jesus said to them, "Watch out, and beware of the yeast of the Pharisees and Sadducees."
They said to one another, "It is because we have brought no bread."
And becoming aware of it, Jesus said, "You of little faith, why are you talking about having no bread?
Do you still not perceive? Do you not remember the five loaves for the five thousand, and how many baskets you gathered?
Or the seven loaves for the four thousand, and how many baskets you gathered?
How could you fail to perceive that I was not speaking about bread? Beware of the yeast of the Pharisees and Sadducees!"
Then they understood that he had not told them to beware of the yeast of bread, but of the teaching of the Pharisees and Sadducees.