Here the 1874 RLDS edition dropped the subject I in the conjoined sentence “and I will go before thee”. The 1908 RLDS edition restored the pronoun. Note that the word order is different in the first and second clauses: will I in the first clause (because of the preceding there) and I will in the second clause.
Summary: Maintain in Ether 1:42 the subject pronoun I in the conjoined sentence “and I will go before thee”.