There are a number of verses which speak of our faith being weak. And other verses when we are weak He is strong. And more verses which says He gives us our faith. Faith is a sign we are saved, not the cause of it. Else we can earn salvation.
So I am convinced our salvation is solely by His grace alone. He chose us, we didn't choose Him.
While salvation is by His grace, our justification comes by faith. Not the same thing. Justification also comes by belief, by love, by our mercy, by our kindness, and more. His Spirit justifies us.
Faith, love, respect, kindness, patience, peace, joy.. these are fruits of His Spirit. His gift. His Spirit compels us and in so doing we are justified, purified and grow in His Spirit. Where the bride purifies herself with water, we are purified by His Spirit.
It is said Faith without works is dead. I add..
Kindness without showing it is dead.
Mercy without giving it is dead.
Love without showing it is dead.
Belief without accepting it is dead.
I mention this not for salvation which we already have, but for our purification as the bride of Christ in preparation for our wedding.
If you are weak in faith but have love, show it. If love seems lost but you are merciful, give it. If mercy evades you but you have patience, be patient. Express what He has given you and more will be added.
Revelation 19:7 Let us rejoice and be glad and give him glory! For the wedding of the Lamb has come, and his bride has made herself ready.