I am a Reformed Pastor and I think the passage most Reformed Christians would turn to is: Ephesians 2: 8-9:
For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— not by works, so that no one can boast.
Much like Catholic teaching referred to above faith is a gift of grace, once your eyes have been opened to the truth, having faith is not seen as work because you don’t do it, rather it would involve work to disbelieve. Often the Reformed will emphasise that it is by grace, through faith, not by faith through grace!