This is what “A Catholic Commentary” (Thomas Nelson & Sons 1953–out of print) has to say about that section:
“Many interpretations are given: (i) he will relentlessly pursue his enemies, halting, but for a moment, to quench his thirst at a wayside brook, then on again, until he lifts his head high as a victor, so NP. (2) Like Samson, worn out by the slaughter, he needs refreshment to raise himself revived; cf. Jg 15:18. (3) The heads of his slain enemies will lie in ditches as if drinking the water there (Boylan). (4) Many of the Fathers see in ‘a’ the humiliation of Christ, and in ‘b’ his exaltation. This seems the best interpretation. ‘lift up the head’ signifies exaltation after humiliation (see 2:4); the drinking ‘of the torrent in the way’ shows that the fight is over.”
Fr. Vincent Serpa, O.P.