These words come from one of the great Welsh Revival Hymns (not the 1904 Revival but an earlier one).
King of heaven and earth by right!
Mighty was He in heaven's purpose,
Mighty, in the pledge to save,
Mighty, from His birth to Calv'ry
Mighty, bursting from the grave.
Still will He
When things hidden now we see.
You can even hear the tune on Youtube complete with pipe organ.