Mat 16:4 A wicked and adulterous generation seeks after a sign; and no sign be given to it, but the sign of the prophet Jonah.

Symbolically, there is a lot going on here below the surface, but it is always interesting to see how Christ describes those of whom he doesn't approve., He doesn't call them "wicked" (as it seems here), "evil," or "bad." This is his most common description, which translates more accurately as"the worthless and unfaithful sorts." These are the people who need to have everything proven and guaranteed to their satisfaction.

Symbolically, however, the key concept here is "the sign of Jonah." Jonah was the prophet who was swallowed by a fish because he didn't want to preach to Israel's enemies in order to save them. Jonah wanted them punished. A parallel is drawn between Jonah spending three nights in the belly of a fish and Christ spending three nights in the heart of the earth, but this parallel misses the contrasting symbolism. The belly and fish are symbols for the physical aspect of life. The heart and the earth are symbols for feeling and emotional relationships. The sign of Jonah refers both to Christ's resurrection and to the problems that this type of people have with anything beyond the physical.

"Wicked" is from ponêros, which is usually translated as "evil" in the NT, but which means "oppressed by toils," "worthless," and "good for nothing."

"Adulterous" is from moichalis, which is from the Greek word for "an adulterous woman." It was also a metaphor for being unfaithful to the gods.

"Generation" is from genea, which means "race," "family," "generation," "class," and "kind." It is a from of the word that we get the scientific "genus" from.

"Seeks" is from epizêteô, which means "to seek after," "to wish," "to miss," and "to request."