I hear this often, especially from the pulpit and I express in my own mind (for my own benefit) each time what I believe so that I don't fall into any erroneous thoughts. It is a simple truth that can become so distorted unless we are taught the whole counsel of God.
If this was all you ever heard I wonder what you would think? Would you think that you were actually saved by your faith? Would you think that it was a work of your own? What about the days that seemingly your faith was but a vapor, would you then think that your salvation was in jeopardy because your faith was weak? (this would be the activity of your faith, a different subject for a different time) Would you be prone to misinterpret 'saved by faith' and make faith into your savior, which would rob Christ of His Glory? I think this happens all the time and I wish that each time this wonderful phrase from the scripture was used, it would include the following:
1. It is God who saves us in Christ Jesus ONLY!
2. It is only the Son of God who satisfies God's eternal wrath against the sins of the elect.
3. Faith is a gift of God by which we, the sheep, know all these truths revealed to us by God the Holy Spirit in the Scriptures. (the sheep hear His voice)
4. It is this precious gift of faith, given to us by God by which we believe and rejoice in the Good News of our accomplished salvation.
So to put it simply....
We are saved by God in Jesus Christ, and we, the redeemed ones, are given the gift of faith by which we are enabled to believe the Gospel and the whole counsel of God.