Shenei Luchot HaBerit
ויהי יצחק בן ארבעים שנה בקחתו את רבקה. Rashi comments on this verse that Abraham on his return from Mount Moriah heard of Rebeccah's birth. Isaac was 37 years old at the time,etc. Why did Rashi have to inform us of these facts? They are spelled out in the Torah!