Sefer HaBahir 8

1[Rabbi Amorai continued,] "And further, why did the Blessed Holy One add the [letter] hey in Abraham [when God changed Abram’s name to Abraham] rather than any other letter? In order that all the organs of man (Adam) will merit life in the world to come, which is compared to the sea [Ed.: Hebrew manuscripts often read "day," but it likely should be "sea." See above, #7]. So to speak, 'With him [Abraham] the building [i.e. - the structure of man] was completed.' As it is written, 'For in the image of Elohim, he made the Adam' (Genesis 9:6). Abraham in gematria is 248, which is the number of the organs of an adam."