There are two times when Jesus says someone has great faith.
Matthew 8:5-13–Centurion who knows Jesus can heal his son without coming to his house.
Matthew 15:21-28–Canaanite woman who says even the dogs get the crumbs from the table.
The commonality is that both these people are Gentiles. Jesus says that He has not seen greater faith than the centurion’s in all Israel. Perhaps verbally acknowledging great faith only in Gentiles is merely another way Jesus seeks to annoy the Jews!
Jesus talks about little faith five times (always directed to Jews, incidentally). The main focus of His comments about little faith are about worrying over life:
Matthew 6:24-30; Luke 12:22-28 about taking no thought for your life;
Matthew 8:24-26 in relation to the fear of the disciples in the storm on the sea;
Matthew 14:28-31 when Peter begins to fear while walking on the water;
Matthew 16:6-11 where the disciples think they are in trouble because they didn’t bring bread with them.
Great faith is a faith that assumes goodness from God without prior leading. In other words, the centurion shows faith by assuming Christ can do miracles from a distance even though no one has ever said anything about this. The Canaanite woman perseveres against Christ’s negative, dismissive words insisting that even she, a Gentile woman, can benefit from Him. Both people act on a belief, not a tested statement.
In little faith, people act directly against what Christ has said. If Christ says God will take care of you, why doubt this?
When we speak of faith, we generally speak of it generically, it’s just a thing you either have or don’t have, like a dog: you either have a dog or you don’t. Having a little dog or a great dog is only something possible for someone who has a dog, though!
There are degrees of faith. We must be careful here not to blame God for our degree of faith, instead, Jesus, God in the flesh, judges men based on their degree of faith. Do we truly trust God?