Olshausen, followed by Cheyne, regards the psalm as made up of two fragments (vv. 1-5 _a_, and 5 _c_-16). But surely the exhortations and promises of the latter portion are most relevant to the summons to the festival contained in the former part, and there could be no more natural way of preparing for the right commemoration of the deliverance than to draw out its lessons of obedience and to warn against departure from the delivering God. Definiteness as to date is unattainable. The presupposed existence of the full Temple ceremonial shows that the psalm was not written in exile, nor at a time of religious persecution. Its warning against idolatry would be needless in a post-exilic psalm, as no tendency thereto existed after the return from captivity. But beyond such general indications we cannot go. The theory that the psalm is composed of two fragments exaggerates the difference between the two parts into which it falls. These are the summons to the feast (vv. 1-5), and the lessons of the feast (vv. 6-16).
Delitzsch suggests that the summons in ver. 1 is addressed to the whole congregation; that in ver. 2 to the Levites, the appointed singers and musicians; and that in ver. 3 to the priests who are intrusted with blowing the Shophar, or horn (Josh. vi. 4, and 2 Chron. xx. 28). One can almost hear the tumult of joyful sounds, in which the roar of the multitude, the high-pitched notes of singers, the deeper clash of timbrels, the twanging of stringed instruments, and the hoarse blare of rams' horns, mingle in concordant discord, grateful to Eastern ears, however unmusical to ours. The religion of Israel allowed and required exuberant joy. It sternly rejected painting and sculpture, but abundantly employed music, the most ethereal of the arts, which stirs emotions and longings too delicate and deep for speech. Whatever differences in form have necessarily attended the progress from the worship of the Temple to that of the Church, the free play of joyful emotion should mark the latter even more than the former. Decorum is good, but not if purchased by the loss of ringing gladness. The psalmist's summons has a meaning still.
The reason for it is given in vv. 4, 5 _a_. It--_i.e._, the feast (not the musical accompaniments)--is appointed by God. The psalmist employs designations for it, which are usually applied to "the word of the Lord"; statute, ordinance, testimony, being all found in Psalms xix., cxix., with that meaning. A triple designation of the people corresponds with these triple names for the feast. _Israel_, _Jacob_, and _Joseph_ are synonyms, the use of the last of these having probably the same force here as in the preceding psalm--namely, to express the singer's longing for the restoration of the shattered unity of the nation. The summons to the feast is based, not only on Divine appointment, but also on Divine purpose in that appointment. It was "a testimony," a rite commemorative of a historical fact, and therefore an evidence of it to future times. There is no better proof of such a fact than a celebration of it, which originates contemporaneously and continues through generations. The feast in question was thus simultaneous with the event commemorated, as ver. 5 _b_ tells. It was God, not Israel, as is often erroneously supposed, who "went forth." For the following preposition is not "from," which might refer to the national departure, but "over" or "against," which cannot have such a reference, since Israel did not, in any sense, go "over" or "against" the land. God's triumphant forth-putting of power over the whole land, especially in the death of the first-born, on the night of the Passover, is meant to be remembered for ever, and is at once the fact commemorated by the feast, and a reason for obeying His appointment of it.
So far the thoughts and language are limpid, but ver. 5 _c_ interrupts their clear flow. Who is the speaker thus suddenly introduced? What is the "language" (lit., lip) which he "knew not"? The explanation implied by the A.V. and R.V., that the collective Israel speaks, and that the reference is, as in Psalm cxiv. 1, to the "strange language" of the Egyptians, is given by most of the older authorities, and by Ewald and Hengstenberg, but has against it the necessity for the supplement "where," and the difficulty of referring the "I" to the nation. The more usual explanation in modern times is that the speaker is the psalmist, and that the language which he hears is the voice of God, the substance of which follows in the remainder of the psalm. As in Job iv. 16 Eliphaz could not discern the appearance of the mysterious form that stood before his eyes, and thus its supernatural character is suggested, so the psalmist hears an utterance of a hitherto unknown kind, which he thus implies to have been Divine. God Himself speaks, to impress the lessons of the past, and to excite the thoughts and feelings which would rightly celebrate the feast. The glad noises of song, harp, and trumpet are hushed; the psalmist is silent, to hear that dread Voice, and then with lowly lips he repeats so much of the majestic syllables as he could translate into words which it was possible for a man to utter. The inner coherence of the two parts of the psalm is, on this explanation, so obvious, that there is no need nor room for the hypothesis of two fragments having been fused into one.