Or HaChaim on Genesis 27:41/אור החיים על בראשית כ״ז:מ״א

1 יקרבו ימי אבל אבי, "the days of mourning for my father are not far off." Esau referred to the time after his father's funeral when the days of mourning commence. He was afraid to murder Jacob before his father would be buried since the dead are reputed to be aware of what goes on as long as the grave or coffin has not been sealed (Shabbat 152).