"Now therefore, my son, obey [my voice]" etc. She said to him: just as all your days you obey me, now too obey me. Another interpretation: she announced to him that he would raise up sons, and there would be no blemish among them; rather, all of them would acknowledge before their father at the time when he called them to tell them what would befall them at the end of days. And the Divine Presence departed from him, and he said to them: my sons, perhaps there is a blemish among you? Immediately they all answered, "Hear, O Israel."
Rebecca Tells Jacob Obey My Voice and the Promise of Untainted Sons
Midrash Aggadah, Genesis 27:8
ועשתה בני שמע וגו'. אמרה לו כשם שכל ימיך אתה שומע לי, עתה ג"כ שמע: ד"א בישרתו שיעמיד בנים ולא יהיה בהם פסול, אלא כולם יודו לפני אביהם בעת שקראם להגיד להם מה יקרה אותם באחרית הימים, ונסתלקה ממנו שכינה, אמר להם בני שמא יש בכם פסול, מיד ענו כולם שמע ישראל: