17 Heb “nations roar, kingdoms shake.” The Hebrew verb הָמָה (hamah, “roar, be in uproar”) is used in v. 3 of the waves crashing, while the verb מוֹט (mot, “overthrown”) is used in v. 2 of mountains tumbling into the sea (see also v. 5, where the psalm affirms that Jerusalem “cannot be moved”). The repetition of the verbs suggests that the language of vv. 2–3 is symbolic and depicts the upheaval that characterizes relationships between the nations of the earth. As some nations (symbolized by the surging, chaotic waters) show hostility, others (symbolized by the mountains) come crashing down to destruction. The surging waters are symbolic of chaotic forces in other poetic texts (see, for example, Isa 17:12; Jer 51:42) and mountains can symbolize strong kingdoms (see, for example, Jer 51:25).
18 Heb “He.” God is the obvious referent here (see v. 5), and has been specified in the translation for clarity.
19 Heb “offers his voice.” In theophanic texts the phrase refers to God’s thunderous shout which functions as a battle cry (see Pss 18:13; 68:33).
20 Or “melts.” See Amos 9:5. The image depicts the nation’s helplessness before Jerusalem’s defender, who annihilates their armies (see vv. 8–9). The imperfect verbal form emphasizes the characteristic nature of the action described.