Jamieson, Fausset and Brown on Isaiah 59:15

15. faileth--is not to be found.

he that departeth ... prey--He that will not fall in with the prevailing iniquity exposes himself as a prey to the wicked (Psa 10:8, 9).

Lord saw it--The iniquity of Israel, so desperate as to require nothing short of Jehovah's interposition to mend it, typifies the same necessity for a Divine Mediator existing in the deep corruption of man; Israel, the model nation, was chosen to illustrate his awful fact.