“This is the legacy of Isaac, Abraham’s son. Abraham begot Isaac” (Genesis 25:19). “This is the legacy of Isaac, Abraham’s son.” “The father of the righteous will exult with happiness [gil yagil], and the begetter of the wise will rejoice in him” (Proverbs 23:24) – happiness [gila] after happiness when the righteous one is born.
“It was in the days of Aḥaz…” (Isaiah 7:1) – Rabbi Hoshaya said: The ministering angels said before the Holy One blessed be He: ‘Master of the universe, woe that Aḥaz reigned.’1Ahaz was a wicked king. See II Kings 16:1–4. He said to them: ‘He is Yotam’s son. His father was righteous, and I cannot extend my hand against him.’
“And the begetter of the wise will rejoice in him” – Rabbi Levi said: From where do you say that anyone who has a son who diligently engages in Torah, that he becomes filled with mercy upon him? The verse states: “My son, if your heart is wise, my heart too will rejoice” (Proverbs 23:15). Rabbi Shimon ben Menasya says: I have derived only the heart of his flesh and blood father, from where is it derived that even the Holy One blessed be He becomes filled with mercy upon him when he diligently engages in Torah?
The verse states: “My heart too2The midrash is explaining that the verse says "too" as a reference to God, who rejoices with him. will rejoice.” Happiness after happiness – when he is a righteous one, son of a righteous one; “this is the legacy of Isaac, Abraham’s son.”