הנה נא זקנתי לא ידעתי יום מותי (תולדות כז:ב)

Why did Yitzchak need to say לא ידעתי יום מותי – that he doesn’t know when he will die? The Gemara says that seven things are hidden from a person. One of them is the day he will die.  However, the Medrash says that Yitzchak knew the time of the Geulah – redemption, even though it’s hidden from people.  One would then think that Yitzchak also knew when he would die. Therefore, Yitzchak said לא ידעתי יום מותי – since the date of his death, he didn’t know.