The hour cometh - in its whole fullness, at Pentecost.
and now is - in its beginnings.
the dead - the spiritually dead, as is clear from Joh 5:28. Here He rises from the calmer phrase “hearing his word” (Joh 5:24), to the grander expression, “hearing the voice of the Son of God,” to signify that as it finds men in a dead condition, so it carries with it a resurrection-power.