If salvation is a completely free gift from God, why are we commanded to "work it out" with fear and trembling?

In this message by Pastor Dennis, we learn about the "paradox of faith." While salvation is a free gift of grace through Jesus, we as believers have a responsibility to actively align our lives with the work God is performing within us.  As we put Christ's teachings into practice, we are building our lives on the Rock, and we will endure life's inevitable storms.