The apostles said, “Increase our faith!” And the Lord said, “If you had faith like a mustard seed, you could say to this mulberry tree, ‘Be uprooted and planted in the sea,’ and it would obey you.”
Just before this, Jesus was talking about the effect sin has on our lives. He was talking about the severity of causing someone else to sin—that one would be better off being cast into the sea with a millstone around his neck than to cause another to sin. This is quite serious, and the disciples were worried about the repercussions of such a sin, and rightly so. Who hasn’t caused another person to sin? I’m certainly guilty of this. So, Jesus says in verses 3-4, rebuke your brother when he sins and forgive him when he repents.
It’s difficult to rebuke someone whose lifestyle does not reflect their position as a child of God, especially when their initial reaction is to defend themselves and rationalise their decisions. It also contradicts human nature to freely forgive someone, even when they are humble enough to apologise. Yet Jesus makes no exceptions. He says, “You must forgive him.”
So, I think it’s safe to say the disciples recognised their own guilt and shame, hence why they asked Jesus for greater faith so that they’d be able to do the things Jesus asks of them. They thought that if they had more faith, they would sin less. And what does Jesus do? Does He lay His hands on them and give them more faith? No, He does not. Instead, He says faith as small as a mustard seed is enough. The size of faith does not matter because God is the one doing the work.
Think of faith as the key to opening the door that brings God into our lives. God gives us that key (Ephesians 2:8-9). Does it matter if you have a bigger key ring? No, it does not; all you need is that one small key you can always use, and He’s the one who has given you the key—the faith—to open the door to salvation. We think that the greater the problem or the greater the illness, the more faith we need, and we beg God to give us more faith.
No, more faith is not the dilemma. Why do you think Jesus stressed so much to have the faith of a child? Because in spite of their inexperience and lack of knowledge, they don’t use their questions to doubt; they merely believe. Jesus didn’t increase the faith of the disciples because faith itself is all we need, no matter how “small” we measure it to be. Jesus does not measure our faith; we either have faith or we don’t, and it is a gift He gives us. That is why even faith as small as a mustard seed has tremendous strength, for Jesus is the actor of our faith.