ליטעראַטור פֿון בית שני אויף בראשית 17:19

[It would bring this passage into harmony with other passages, if what Philo wrote was ἐκλιπὸν … ἀποθανὸν … μεταδίωκον (all in agreement with γένος), and χαρὰς καὶ εὐφροσύνας. It would seem not unlikely that a scribe, a little puzzled by the neuters ἐκλιπὸν and ἀποθανόν, and seeing ἐκλιπόντ- and ἀποθανόντ- before him, filled in the -ων in each word, producing ἐκλιπόντων and ἀποθανόντων. This led to the change of χαρὰς καὶ εὐφροσύνας into genitives singular. With ἑκλιπόν and ἀποθανόν restored, the construction is the same as that in De Somniis, i. 68 ᾦ τὸ αὐτομαθὲς γενός, Ισαάκ, ἐνδιαιγᾶται, μηδέποτε … ἀφιστάμενον. Our passage is also illustrated by De Mut. Nom. 1 ᾗ τὸ αὐτομαθὲς ἐπέλαμψε γένος, Ἰσαάκ, εὐπαθειῶν ἀρίστη, χαρά, and Quod Det. 46 τὸ μόνον ἀπαθὲς εἶδος ἐν γενέσει τὸν Ἰσαάκ and De Mut. Nom. 261 τέξεται οὖν σοι ἡ ἀρετὴ υἱὸν γενναῖον ἄρρενα (Gen. 17:19) παντὸς ἀπηλλαγμένον θήλεος πάθους.

[253] What then does God in His kindness do? Abraham had asked for one thing, God gives him two. He had prayed for the less, God grants him the greater. He said to him, we read, “Yes, Sarah thy wife shall bear a son” (Gen. 17:19). How significant is that answer “Yes,” fraught as it is with inner meaning. For what can be more befitting to God than to grant and promise His blessings in a moment and with a sign of assent?