וְהִתְבָּרֲכ֣וּ בְזַרְעֲךָ֔ כֹּ֖ל גּוֹיֵ֣י הָאָ֑רֶץ עֵ֕קֶב אֲשֶׁ֥ר שָׁמַ֖עְתָּ בְּקֹלִֽי׃
En tu simiente serán benditas todas las gentes de la tierra, por cuanto obedeciste á mi voz.
The Midrash of Philo
Why did Abraham appear to hesitate about the promise, for the sacred writer says, He said in his mind, shall there be a son to one who is a hundred years old; and shall Sarra, who is ninety years old, bring forth a child? (Genesis 22:18).