Rashi on Genesis 30:25/רש"י על בראשית ל׳:כ״ה

1כאשר ילדה רחל את יוסף WHEN RACHEL HAD BORN JOSEPH — after the birth of him who was to become Esau’s adversary (Genesis Rabbah 73:7) — as it is said (Obadiah 1:18) “And the house of Jacob shall be a fire, and the house of Joseph a flame and the house of Esau for stubble“. Fire (Jacob) that has no flame (Joseph) has no effect at a distance. Therefore, when Joseph was born Jacob put his trust in the Holy One, blessed be He, and wished to return home (Obadiah 1:18).