In his sermon “The Law and the Promise,” Tim Keller offers his response to those who come asking, “How much do I have to trust God in order to be saved?”
If you are about to fall off a cliff, maybe you’ve already fallen, you’re falling off and you’re on your way to your death, you look up and see a branch sticking out of the side of the cliff, you look up at that thing, and I want to know, “How much faith do you have to have in order for it to save you?”
The answer is, “Just enough faith to grab it.” Because, your faith does not save you at all. It’s not the strength of your faith…it would be the strength of the branch that would save you, not the strength of your faith. If the branch is strong enough to save you, you’re saved.
It is not the quality of your faith, but the object of your faith, that saves you. Trust in God, who is mighty to save.