John Calvin Commentary Genesis 25:9

"And Isaac and Ishmael his sons buried him in the cave of Machpelah, in the field of Ephron the son of Zohar the Hittite, which is before Mamre." — Genesis 25:9 (ASV)

And his sons Isaac and Ishmael buried him. From this it appears that although Ishmael had long ago been dismissed, he was not utterly alienated from his father, because he performed the duty of a son in celebrating the funeral rites of his deceased parent. Ishmael, rather than the other sons, did this, since he was nearer.