Shall cleave (kollhqhsetai). First future passive, "shall be glued to," the verb means. The twain shall become one flesh (esontai oi duo ei sarka mian). This use of ei after eimi is an imitation of the Hebrew, though a few examples occur in the older Greek and in the papyri. The frequency of it is due to the Hebrew and here the LXX is a direct translation of the Hebrew idiom.