Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
Greeting to Him Who Is Become Known in Righteousness and Salvation
This is the only Psalm which is inscribed מזמור without further addition, whence it is called in B. Aboda Zara, 24b, מזמורא יתומא (the orphan Psalm). The Peshמto Syriac inscribes it De redemtione populi ex Aegypto; the "new song," however, is not the song of Moses, but the counterpart of this, cf. Rev 15:3. There "the Lord reigneth" resounded for the first time, at the sea; here the completion of the beginning there commenced is sung, viz., the final glory of the divine kingdom, which through judgment breaks through to its full reality. The beginning and end are taken from Psa 96:1-13. Almost all that lies between is taken from the second part of Isaiah. This book of consolation for the exiles is become as it were a Castalian spring for the religious lyric.
Psa 98:1 we have already read in Psa 96:1. What follows in Psa 98:1 is taken from Isa 52:10; Isa 63:5, cf. Psa 98:7, Psa 59:16, cf. Psa 40:10. The primary passage, Isa 52:10, shows that the Athnach of Psa 98:2 is correctly placed. לעיני is the opposite of hearsay (cf. Arab. l-l-‛yn, from one's own observation, opp. Arab. l-l-chbr, from the narrative of another person). The dative לבית ישראל depends upon ויּזכּר, according to Psa 106:45, cf. Luk 1:54.
The call in Psa 98:4 demands some joyful manifestation of the mouth, which can be done in many ways; in Psa 98:5 the union of song and the music of stringed instruments, as of the Levites; and in Psa 98:6 the sound of wind instruments, as of the priests. On Psa 98:4 cf. Isa 44:23; Isa 49:13; Isa 52:9, together with Isa 14:7 (inasmuch as פּצחוּ ורננוּ is equivalent to פּצחוּ רנּה). קול זמרה is found also in Isa 51:3.
Here, too, it is all an echo of the earlier language of Psalms and prophets: Psa 98:7 = Psa 96:11; Psa 98:7 like Psa 24:1; Psa 98:8 after Isa 55:12 (where we find מחא כּף instead of the otherwise customary תּקע כּף, Psa 47:2; or הכּה כּף, Kg2 11:12, is said of the trees of the field); Psa 98:9 - Psa 96:13, cf. Psa 36:10. In the bringing in of nature to participate in the joy of mankind, the clapping rivers (נהרות) are original to this Psalm: the rivers cast up high waves, which flow into one another like clapping hands;
(Note: Luther renders: "the water-floods exult" (frohlocken); and Eychman's Vocabularius predicantium explains plaudere by "to exult (frohlocken) for joy, to smite the hands together prae gaudio;" cf. Luther's version of Eze 21:17.)
cf. Hab 3:10, where the abyss of the sea lifts up its hands on high, i.e., causes its waves to run mountain-high.