Gregory the Great
Catena Aurea · Lukasevangelium 17
Lk 17, Verses 5–6English original
And the apostles said unto the Lord, Increase our faith. And the Lord said, If ye had faith as a grain of mustard seed, ye might say unto this sycamine tree, Be thou plucked up by the root, and be thou planted in the sea; and it should obey you.
(22. Mor. c. 21.) That is, that the faith which has already been received in its beginning, might go on increasing more and more unto perfection.