The 1981 LDS edition reinterpreted upon as two words, up on, although I can detect very little, if any, semantic difference between “raised upon his hands” and “raised up on his hands”. Elsewhere in the text, there are no other examples referring to “upon one’s hands” or “up on one’s hands”. But somewhat parallel to this example here in Ether 15:31 are eight examples in the text that refer to someone rising up to stand on their feet:
All these examples have the single word upon, not up on (although we should note that there is the one example, in 3 Nephi 20:2, of up upon). All this suggests that the spelling up on in the 1981 LDS edition for Ether 15:31 is textually doubtful.
In this passage the 1874 RLDS edition replaced the preposition upon with up, giving “Shiz raised up his hands”. This reading provides an alternative for Shiz’s last physical motion prior to collapsing and dying. Nonetheless, this textual change was probably unintentional, although it is possible as a reading (which probably explains why it was copied into the 1892 RLDS edition). The 1908 RLDS edition restored the original upon to the RLDS text. Like the phrase “to raise upon one’s hands”, the phrase “to raise up one’s hands” is unique in the history of the Book of Mormon text. Since either reading will work, at least in theory, the critical text will accept the earliest reading, “Shiz raised upon his hands”.
Summary: Restore the single-word spelling upon in Ether 15:31 (“Shiz raised upon his hands”); the original text here very likely read upon rather than up, the reading of the 1874 RLDS edition.