Trust ye in Jehovah for ever. As to the words, some read in the second clause, "Trust in God, the strong Jehovah of ages;" but as tsvr (tzur) is not always an adjective, but signifies strength, I reject that meaning as forced, besides that it has little relation to the subject, as will immediately appear. There is also little ground for the ingenuity of those who infer from this passage the divinity of Christ, as if the Prophet said, that "Jehovah is in Jah;" for the twofold name of God is given for the express purpose of magnifying his power. He now exhorts the people to rest safely on God, and therefore, after the preceding doctrine, there is now room for exhortation. Besides, it would have been vain to say that our peace is in the hand of God, and that he is our faithful guardian, if we had not been taught and instructed on this subject, and at the same time urged by exhortations. Yet he exhorts us not only to earnest hope, but to perseverance; and this discourse applies properly to believers, who have already learned what it is to trust in the Lord, and who need to be strengthened, because they are still weak, and may often fall, in consequence of the various motives to distrust with which they are called to struggle. He therefore does not enjoin them merely to trust in the Lord, but to remain steadfastly in trust and confidence to the end. For in Jah Jehovah is the strength of ages. [1] We ought to attend to the reason which is here assigned, namely, that as the power of God, which is the object of faith, is perpetual, so faith ought to be extended so as to be equally perpetual. When the Prophet speaks of the strength and power of God, he does not mean power which is unemployed, but power active and energetic, which is actually exerted on us, and which conducts to the end what he had begun. And this doctrine has a wider application, for it bids us truly believe that we ought to contemplate the nature of God; for, as soon as we turn aside from beholding it, nothing is seen but what is fleeting, and then we immediately faint. Thus ought faith to rise above the world by continual advances; for neither the truth, nor the justice, nor the goodness of God, is temporary and fading, but God continues always to be like himself.

Footnotes

1 - "For in the Lord Jehovah is (Heb. the Rock of ages) everlasting strength." -- Eng. Ver.

Trust ye in the Lord for ever - The sense is, 'Let your confidence in God on no occasion fail. Let no calamity, no adversity, no persecution, no poverty, no trial of any kind, prevent your reposing entire confidence in him.' This is spoken evidently in view of the fact stated in the previous verse, that the mind that is stayed on him shall have perfect peace.
For in the Lord Jehovah - 'This is one of the four places where our translators have retained the original word Yahweh (compare Exodus 6:3; Psalm 133:1-3 :18; the notes at Isaiah 12:2). The original is יהוה ביה beyâhh yehovâh; the first word, יה yâhh, (compare Psalm 68:4), being merely an abridged form of Yahweh. The same form occurs in Isaiah 12:2. The union of these two forms seems designed to express, in the highest sense possible, the majesty, glory, and holiness of God; to excite the highest possible reverence where language fails of completely conveying the idea.
Is everlasting strength - Hebrew as in the Margin, 'The rock of ages;' a more poetic and beautiful expression than in our translation. The idea is, that God is firm and unchangeable like an eternal rock; and that in him we may find protection and defense for everlasting ages (see Deuteronomy 32:4, et al.; 1-Samuel 2:2; 2-Samuel 22:32, 2-Samuel 22:47; 2-Samuel 23:3; Psalm 18:31; Psalm 19:14; Psalm 28:1; Psalm 42:9; Psalm 62:2, Psalm 62:6-7,, where God is called 'a rock').

In the Lord Jehovah "In Jehovah" - In Jah Jehovah, Hebrews.; but see Houbigant, and the note on Isaiah 12:2 (note).
Everlasting strength - צור עולמים tsur olamim, "the rock of ages; "or, according to Rab. Maimon, - the eternal Fountain, Source, or Spring. Does not this refer to the lasting streams from the rock in the desert? And that rock was Christ. ge han hoped in the Lord fro the everlastinge worldis. - Old Ms. Bible.

Trust ye in the Lord for ever,.... In the Word of the Lord for ever and ever, as the Targum again; that is, at all times, in every state and condition, in times of affliction, temptation, and darkness; for he will support under, and in his own time deliver out of every trouble, and cause all things to work to gether for good; and trust in him always, for everything, for all temporal blessings, and for all spiritual ones, and for eternal life and happiness; for he has them, has promised them, and will give them:
for in the Lord JEHOVAH is everlasting strength; Christ is the Lord JEHOVAH, which is, and was, and is to come, self-existent, eternal, and immutable; and in him is strength, as well as righteousness for his people; and that for everything it is wanted for, to bear up under temptations and afflictions, to withstand every spiritual enemy, to exercise every grace, and discharge every duty: and this strength is everlasting; it always continues in him, and is always to be had from him; he is the "eternal" God, who is the refuge of his people, and his "arms" of power and might "underneath" them are "everlasting": the words may be rendered, "for in Jah" is "Jehovah, the Rock of ages" (q); Jehovah the Son is in Jehovah the Father, according to John 10:38 or "Jah Jehovah" is "the Rock of ages", so Vitringa; he is the "Rock" on which the church and every believer is built, against which "the gates of hell cannot prevail"; and he has been the Rock of his people in ages past, and will be in ages to come: or "of worlds"; this world, and that to come; and so it is explained in the Talmud (r), he that trusts in the Lord has a refuge in this world, and in the world to come.
(q) "in Jah est Jehovah, rupes saeculorum". (r) T. Bab. Menachot, fol. 29. 2.

Lord JEHOVAH--Hebrew, Jah, Jehovah. The union of the two names expresses in the highest degree God's unchanging love and power (compare Psalm 68:4). This passage, and Isaiah 12:2; Exodus 6:3; Psalm 83:18, are the four in which the English Version retains the JEHOVAH of the original. MAURER translates, "For JAH (the eternal unchangeable One, Exodus 3:14) is JEHOVAH, the rock of ages" (compare Isaiah 45:17; Deuteronomy 32:15; 1-Samuel 2:2).

A cry goes forth again, as if from heaven, exhorting Israel to continue in this mind. "Hang confidently on Jehovah for ever: for in Jah, Jehovah, is an everlasting rock." The combination Jah Jehovah is only met with here and in Isaiah 12:2. It is the proper name of God the Redeemer in the most emphatic form. The Beth essentiae frequently stands before the predicate (Ges. 151, 3); here, however, it stands before the subject, as in Psalm 78:5; Psalm 55:19. In Jah Jehovah (munach, tzakeph) there is an everlasting rock, i.e., He is essentially such a rock (compare Deuteronomy 32:4, like Exodus 15:2 for Isaiah 12:2).

For ever - In all times and conditions.