Faith is a work if you are not talking about faith given in regeneration, a fruit of the Spirit. But if you faith by the unregenerate person, its a law work
Matt 23:23
23 Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith: these ought ye to have done, and not to leave the other undone.
So do you mean faith of regeneration or required faith of the law ?