Faith never justifies us. Only God does. The Confession of Faith makes the same point. In the same way as a carpenter's tools are a hammer and a saw, and a farmer's tools are a tractor and a plow, so the Christian's tool is faith. Faith is the tool, the instrument, that God uses to bring us to Himself.
Many people misunderstand faith.
They think of faith as some kind of good work which God admires and rewards with salvation. If you only have faith, or enough faith, then you will be accepted and glorified. It is an instrument, a tool, used by God for us to accept our acceptance. You drive your car over the Golden Gate Bridge with perfect faith that it will hold you, and you arrive safely on the other side. With just as good faith you may drive onto some wooden bridge over a country stream, but if the boards are decayed you will crash through and fall into the stream.