14 “You have cleft the fountains and torrents”: in order that they might flow with the stream of wisdom, might flow with the riches of the faith, might water the saltness of the Gentiles, in order that they might convert all unbelievers into the sweetness of the faith by their watering....In some men the Word of God becomes a well of water springing up unto life eternal; but others hearing the Word, and not so keeping it as that they live well, yet not keeping silence with tongue, they become torrents.
For they are properly called torrents which are not perennial: for sometimes also in a secondary sense torrent is used for river: as has been said, “with the torrent of Your pleasures You shall give them to drink.” For that torrent shall not ever be dried up. But torrents properly are those rivers named, which in summer fail, but with winter rains are flooded and run. You see therefore a man sound in faith, that will persevere even unto the end, that will not forsake God in any trial; for the sake of the truth, not for the sake of falsehood and error, enduring all difficulties.
Whence is this man so vigorous, but because the Word has become in him a well of water springing up unto life eternal? But the other receives the Word, he preaches, he is not silent, he runs: but summer proves whether he be fountain or torrent. Nevertheless through both be the earth watered, by Him who has wrought Salvation in the midst of the earth: let the fountains overflow, let the torrents run.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)