Matthew 21:30

This passage is translated from the earliest manuscripts. Later manuscripts made a real hack job of the passage.

The word used here is not "repentance":

"Rather “changed his mind,” felt regret but not repentance or Metanoia, a deeper and more lasting feeling: see ch. Matthew 3:2.

According to a well-supported reading the cases of the two sons are reversed. The first agrees but goes not, the second refuses but afterwards works in the vineyard. The variation is interesting, because it points to an interpretation by which the two sons represent Jew and Gentile"

(Cambridge Bible for Schools and Colleges)

Strongs #G3338, "μεταμέλομαι" (metamelomai) means "to change one's care or interest for another," implying a change of mind or repentance characterized by regret or sorrow. It denotes a reconsideration or remorseful reflection on past actions or decisions.