The size of faith doesn’t matter because God is the one doing the moving.
If it is my faith that moved the mountain, then the bigger the mountain the more faith I would need to move it.

The bigger the obstacle the more strength I’d need to climb it.

The more serious the illness a faith even greater would be required to overcome it.

The more serious the sin the more faith I would need in order to have it forgiven.

That kind of thinking kind of makes sense, but that’s not how faith works. In fact, faith doesn’t do the work at all. And thank God for that.

God is the one doing the work through faith. Think of faith as the key that opens the door to God acting in our lives. If I have a bigger key ring than you do, does it matter? The size of a key ring doesn’t matter – key rings don’t open doors but it’s that little key on the ring that opens doors. Even a little faith opens the door for God to move the mountains and trees and even our hearts.

Vince Gerhardy, Faith the Size of a Mustard Seed