The apostles said to the Lord,“Increase our faith!” 6 And the Lord answered, “If you have faith the size of a mustard seed, you can say to this mulberry tree, ‘Be uprooted and planted in the sea,’ and it will obey you
It’s clear Christ is not responding to the immediate request but to something presupposed to it. Presumably the Apostles want their faith increased because they judge they don’t have enough of it to get something done or resist some trial, and Christ is attacking the assumption that any amount of faith would need access to a greater amount of power. One’s faith comes by grace and grace has already transformed the soul into a son of omnipotence. From the moment of baptism, or even from the first moment the soul efficaciously desires baptism, the soul is elevated above all natural goods and has, by grace, its evidence that it is loved by God beyond the love of any lovers, parents or friends. One can make sense of asking for grace but not of asking it to have access to greater power.
While there is clearly a sense in which faith and the life of grace start small and grow, this seems to consist in our recognition of and assimilation to the infinite power and love that has been there from the beginning and not in God, as it were, starting with tiny and feeble gifts before working up to ones that can actually get things done.