In the Book of Moses original manuscript, Moses 1:3 reads:
And God spake unto Moses, saying, Behold I, I am the Lord God Almighty, and Endless is my name.
Moses 4:1 similarly reads:
That Satan, whom thou hast commanded in the name of mine Only Begotten, is the same which was from the beginning, and he came before me, saying—Behold I, send me, I will be thy son, and I will redeem all mankind, that one soul shall not be lost.
This curious wording is not what we would expect in English, however Kent P. Jackson explains:
In my judgment, the best explanation for “Behold I” is found in the grammar of the Hebrew Bible. The Hebrew construction hinĕnî is found in about 180 locations in the Old Testament. It means “Behold I.” The construction contains the word hinnēh, “behold,” to which is affixed the suffix -nî, which is a first-person-singular pronoun. The word hinnēh does not translate easily into today’s English. It is not a verb and thus does not mean “behold” in the sense of “to look” or “to see.” It can be described best as an exclamatory particle that has the purpose of drawing the attention of the hearer to the speaker. In some places in the King James Version, it is translated with the English word lo, a nonverbal exclamatory that reproduces better the intent of the Hebrew, as in “Lo, I die” (Gen. 50:5).– Kent P. Jackson – Behold I
That the unexpected combination “Behold I” appears in two places in the Joseph Smith Translation of Genesis suggests strongly that neither occurrence was a scribal error or an inadvertent misstatement by Joseph Smith. The Prophet is not recorded elsewhere as ever having employed such a construction, and thus it is unlikely that it represents his own speech pattern. Moreover, it is not a construction that is found in the Book of Mormon or in the King James Version of the Bible.13 Consistent with English usage, “Behold I” was translated out of the English Bible, just as it was edited out of the book of Moses. Whereas the King James translation was a significant model for the language of the Prophet’s revelations and translations, it clearly was not the model for “Behold I.” I suggest that both occurrences of “Behold I” in the New Translation were once in the Hebrew text of Genesis—in passages that were lost since antiquity but were restored anew through the Prophet Joseph Smith.– Kent P. Jackson – Behold I
Where would Joseph Smith have learned this kind of Hebrew language?