זוהר בראשית — דף רנא ע”א

The land of Canaan and Egypt decompose the body quickly, therefore they embalmed the body of Jacob to preserve it. The oil placed on the navel is absorbed inside and maintains the body from within. The body of Jacob needed to be preserved because it is the body of the patriarchs. There are places whose holiness is more conducive to the burial of the dead, and burial in the Land of Israel is the most elevated of all lands.