Never Abandoning a Wayward Child

Never Abandoning a Wayward Child:
Sefer Tzemach Dovid asks: This seems to be the same question the wicked son asks, and he is chastised for saying that the avodah is “for you” and not for him. If so, why is the word “v’haya” used here, as this word always connotes joy (Bereishis Rabbah 42:3).
He answers by quoting Chazal (see Pesachim 49B and Bava Kama 119A), who say that a father is commanded never to push away a wayward son because his offspring might be good. Therefore, the word v’haya is used to teach us that one should show joy to all of his children, even if they are not going in the proper way, because they may have upright children.