The thought is fixed; thou wilt keep peace, peace. [1] As the Hebrew word ytsr (YEtzEr) signifies both "imagination" or "creature," and "thought," some render it, "By a settled foundation thou wilt keep peace;" as if the Prophet meant, that when men, amidst the convulsions of the world, continue to rest firmly on God, they will always be safe. Others render it, "For the fixed thought thou wilt keep peace;" which amounts to nearly the same thing, that they who have fixed their minds on God alone will at length be happy; for in no other way does God promise that he will be the guardian of his people than when they rely on his grace with settled thoughts, and without change or wavering. Since, however, the sign of the dative case is not added, but the Prophet in a concise manner of expression says, "Fixed or steadfast thought," let my readers judge if it be not more appropriate to view it as referring to God, so as to make the meaning to be, that the peace of the Church is founded on his eternal and unchangeable purpose; for, in order to prevent godly minds from continual wavering, it is of the highest importance to look to the heavenly decree. It is undoubtedly true that we ought constantly to hope in God, that we may perceive his continual faithfulness in defending us; and believers are always enjoined not to be driven about by any doubt, or uncertainty, or wavering, but firmly to rely on God alone. Yet the meaning which is more easily obtained from this passage, and comes more naturally from the words of the Prophet, is, that it is a fixed and unchangeable decree of God, that all who hope in him shall enjoy eternal peace; for if fixed thought means the certainty and steadfastness of the godly, it would be superfluous to assign the reason, which is -- Because he hath trusted in thee. In short, both modes of expression would have been harsh, that "continual peace is prepared for imagination," or "for thought." But it is perfectly appropriate to say that, when we trust in God, he never disappoints our hope, because he has determined to guard us for ever. Hence it follows, that, since the safety of the Church does not depend on the state of the world, it is not moved or shaken by the various changes which happen daily; but that, having been founded on the purpose of God, it stands with steady and unshakable firmness, so that it can never fall. There is also, I think, an implied contrast between God's fixed thought and our wandering imaginations; for at almost every moment there springs up something new which drives our thoughts hither and thither, and there is no change, however slight, that does not produce some doubt. We ought therefore to hold this principle, that we do wrong if we judge of God's unshaken purpose by our fickle imaginations; as we shall elsewhere see, "As far as the heavens are from the earth, so far are my thoughts from your thoughts, O house of Israel." (Isaiah 55:9.) We ought therefore above all to hold it certain, that our salvation is not liable to change; because the purpose of God is unchangeable. Thou wilt keep peace, peace. What has now been stated explains the reason of the repetition of the word peace; for it denotes uninterrupted continuance for ever. By the word peace I understand not only serenity of mind, but every kind of happiness; as if he had said, that the grace of God alone can enable us to live prosperously and happily.

Footnotes

1 - "Thou wilt keep him in perfect peace (Heb. peace, peace) whose mind (or, thought, or, imagination) is stayed on thee." -- Eng. Ver.

Thou wilt keep him - The following verses to Isaiah 26:11, contain moral and religious reflections, and seem designed to indicate the resignation evinced by the 'righteous nation' during their long afflictions. Their own feelings they are here represented as uttering in the form of general truths to be sources of consolation to others.
In perfect peace - Hebrew as in the Margin, 'Peace, peace;' the repetition of the word denoting, as is usual in Hebrew, emphasis, and here evidently meaning undisturbed, perfect peace. That is, the mind that has confidence in God shall not be agitated by the trials to which it shall be subject; by persecution, poverty, sickness, want, or bereavement. The inhabitants of Judea had been borne to a far distant land. They had been subjected to reproaches and to scorn Psalm 137:1-9; had been stripped of their property and honor; and had been reduced to the condition of prisoners and captives. Yet their confidence in God had not been shaken. They still trusted in him; still believed that he could and would deliver them. Their mind was, therefore, kept in entire peace. So it was with the Redeemer when he was persecuted and maligned (1-Peter 2:23; compare Luke 23:46). And so it has been with tens of thousands of the confessors and martyrs, and of the persecuted and afflicted people of God, who have been enabled to commit their cause to him, and amidst the storms of persecution, and even in the prison and at the stake, have been kept in perfect peace.
Whose mind is stayed on thee - Various interpretations have been given of this passage, but our translation has probably hit upon the exact sense. The word which is rendered 'mind' (יצר yētser) is derived from יצר yâtsar to form, create, devise; and it properly denotes that which is formed or made Psalm 103:14; Isaiah 29:16, Hebrews 2:18. Then it denotes anything that is formed by the mind - its thoughts, imaginations, devices Genesis 8:21; Deuteronomy 31:21. Here it may mean the thoughts themselves, or the mind that forms the thoughts. Either interpretation suits the connection, and will make sense. The expression, 'is stayed on thee,' in the Hebrew does not express the idea that the mind is stayed on God, though that is evidently implied. The Hebrew is simply, whose mind is stayed, supported (סמוּך sâmûk); that is, evidently, supported by God. There is no other support but that; and the connection requires us to understand this of him.

In perfect peace - שלום שלום shalom, shalom, "peace, peace, "i.e., peace upon peace - all kinds of prosperity - happiness in this world and in the world to come.
Because he trusteth in thee "Because they have trusted in thee" - So the Chaldee, בטחו betacho. The Syriac and Vulgate read בטוח batachnu, "we have trusted. "Schroeder, Gram. Hebrews p. 360, explains the present reading בטוח batuach, impersonally, confisum est.

Thou wilt keep [him] in perfect peace, [whose] (d) mind [is] stayed [on thee]: because he trusteth in thee.
(d) You have decreed so, and your purpose cannot be changed.

Thou wilt keep him in perfect peace,.... Peace with God in Christ through his blood, in a way of believing, and as the fruit and effect of his righteousness being received by faith; this is not always felt, received, and enjoyed in the soul; yet the foundation of it always is, and is perfect; and besides, this peace is true, real, and solid; in which sense the word "perfect" is used, in opposition to a false and imaginary one; and it will end in perfect peace in heaven: moreover, the word "perfect" is not in the Hebrew text, it is there "peace, peace"; which is doubled to denote the certainty of it, the enjoyment of it, and the constancy and continuance of it; and as expressive of all sorts of peace, which God grants unto his people, and keeps for them, and them in; as peace with God and peace with men, peace outward and peace inward, peace here and peace hereafter; and particularly it denotes the abundance of peace that believers will have in the kingdom of Christ in the latter day; see Psalm 72:7,
whose mind is stayed on thee; or "fixed" on the love of God, rooted and grounded in that, and firmly persuaded of interest in it, and that nothing can separate from it; on the covenant and promises of God, which are firm and sure; and on the faithfulness and power of God to make them good, and perform them; and on Christ the Son of God, and Saviour of men; upon him as a Saviour, laying the whole stress of their salvation on him; upon his righteousness, for their justification; upon his blood and sacrifice, for atonement, pardon, and cleansing; on his fulness, for the supply of their wants; on his person, for their acceptance with God; and on his power, for their protection and preservation; see Isaiah 10:20,
because he trusteth in thee; not in the creature, nor in any creature enjoyment, nor in their riches, nor in their righteousness, nor in their own hearts, nor in any carnal privileges: only in the Lord, as exhorted to in the next verse Isaiah 26:4; in the Word of the Lord, as the Targum, that is, in Christ.

mind . . . stayed-- (Psalm 112:7-8). Jesus can create "perfect peace" within thy mind, though storms of trial rage without (Isaiah 57:19; Mark 4:39); as a city kept securely by a strong garrison within, though besieged without (so Philippians 4:7). "Keep," literally, "guard as with a garrison." HORSLEY translates, (God's) workmanship (the Hebrew does not probably mean "mind," but "a thing formed," Ephesians 2:10), so constantly "supported"; or else "formed and supported (by Thee) Thou shalt preserve (it, namely, the righteous nation) in perpetual peace."

The relation of Israel and Jehovah to one another is now a permanent one. "Thou keepest the firmly-established mind in peace, peace; for his confidence rests on Thee." A gnome (borrowed in Psalm 112:7-8), but in a lyrical connection, and with a distinct reference to the church of the last days. There is no necessity to take סמוּ יצר as standing for יצר סמוּך, as Knobel does. The state of mind is mentioned here as designating the person possessing it, according to his inmost nature. יצר (the mind) is the whole attitude and habit of a man as inwardly constituted, i.e., as a being capable of thought and will. סמוּך is the same, regarded as having a firm hold in itself, and this it has whenever it has a firm hold on God (Isaiah 10:20). This is the mind of the new Israel, and Jehovah keeps it, shâlom, shâlom (peace, peace; accusative predicates, used in the place of a consequential clause), i.e., so that deep and constant peace abides therein (Philippians 4:7). Such a mind is thus kept by Jehovah, because its trust is placed in Jehovah. בּטוּח refers to יצר, according to Ewald, 149, d, and is therefore equivalent to הוּא בּטוּח (cf., Psalm 7:10; Psalm 55:20), the passive participle, like the Latin confisus, fretus. To hang on God, or to be thoroughly devoted to Him, secures both stability and peace.