Jamieson, Fausset and Brown on John 5:25-29

25-29. The hour cometh--in its whole fulness, 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.

shall live--in the sense of Joh 5:24.