It said above (24:36) that Avraham gave to Yitzchak all that he owned. Why did the Torah repeat this here?
Rashi: It includes Birkas Daitiki, with reference to the Berachah which Hashem gave to Avraham, enabling him to bless whoever he wished. 1
R. Chaim Paltiel: Before, Avraham gave the permanent rights to the property, but kept the Peros for himself. Now he gave even the Peros.
Avraham lived 35 years after he sent Eliezer. He had acquired more property in that time. (PF) 2
Why did he give everything to Yitzchak? One should not divert inheritance, even from a bad son to a good son (Kesuvos 53a)!
Rosh, Moshav Zekenim (10) #1: Avraham and Yishmael were converts. A convert does not inherit a convert. Also Da'as Zekenim, Hadar Zekenim say so, and add that Avraham already gave everything to Yitzchak (24:36) before Bnei Keturah were born. 1
R. Chaim Paltiel, Moshav Zekenim (10) #2: Sarah had said (21:10) that Hagar's son will not inherit with Yitzchak, and Hashem told Avraham to heed her. Avraham learned from "Ki v'Yitzchak Yikarei Lecha Zara" that only Yitzchak should inherit (Kli Yakar).
רש"י: הברכות מסורות בידך...ואברהם מסרם ליצחק: למה לא פירש כפשוטו שנתן ליצחק את כל רכושו?
גור אריה: את כל רכושו נתן לו כבר קודם [כשהלך אליעזר לחרן].