en_tn_condensed/mat/12/39.md

An evil and adulterous generation seeks for a sign ... given to it

Jesus is speaking to his present generation. Alternate translation: "You are an evil and adulterous generation who demands signs from me ... given to you" (See: rc://en/ta/man/translate/figs-123person)

adulterous generation

Here "adulterous" is a metaphor for people who are not faithful to God. Alternate translation: "unfaithful generation" or "godless generation" (See: rc://en/ta/man/translate/figs-metaphor)

no sign will be given to it

Jesus would not give them a sign because, though he had already performed many miracles, they refused to believe him. This can be stated in active form. Alternate translation: "I will not give it a sign" or "God will not give you a sign" (See: rc://en/ta/man/translate/figs-activepassive)

except the sign of Jonah the prophet

"except the same sign God gave to Jonah the prophet"