He describes what mercy would do, even that God would at length restore the captives and bring them back from exile to their own country. There was however mention made previously of his favor, that we may know that the people were restored for no other reason but because God had mercy on them. The Prophet then having pointed out the fountain of redemption, passes on now to the external effect, by which God proved that he was reconciled to his people. Hence he says, set up for thee titles

We must first understand why the Prophet speaks thus. When the Jews were led away into Chaldea, they thought that a return was closed up against them. Having then given up every concern for their country, they dwelt among foreign nations, as though they were dead to the land of Canaan. They knew that they had forfeited that land; but they did not understand what had been so often said to them by the Prophets, that their punishment was to be temporary. As they had before disregarded all threatenings, so when God began to fulminate against them, despair overwhelmed their minds, so that they did not wish to hear anything about a return. As then they thought that they were never to return to their own country, they had forgotten the way. As when one moves to another place where he intends to dwell all his life, he only seeks to know the way thither, but does not observe the accommodations on the road, in order to use them again, nor does he take notice which way he goes, whether he turns here to the right and there to the left; it is enough for him to reach the place to which he is going; so also it was with the Jews; they had made up their minds to remain in perpetual exile, they were not therefore solicitous about the road, so as to remember their journey. Therefore the Prophet says now, Set up for thee titles, or inscriptions; for those who travel anywhere, if they mean to return, know that such an inn was commodious, and also that there was so much distance between this town or city and that village, and in like manner, that the road was straight or turned more to one side than another. When therefore they think of a return, they attend to such things as these.

It is for this purpose that the Prophet says, Set up for thee titles, that is, that thou mayest assist thy memory, as travelers are wont to do, who intend to return by the same way. Set up then for thee titles, and raise up for thee heaps, or stones, which we call in our language monioyes; as though he had said, “Thou indeed hast hitherto thought that the way has been closed up against thee, so that thou art to return no more: but God will stretch forth his hand and restore thee to thy former state.” We hence see that the similitude is taken from the common practice of men, but employed for this end, that the Jews might not despair of their restoration as they had previously don. ⁴²⁴²    
   Raise up for thyself heaps, Fix for thyself pillars.
   Instead of צינים many copies read ציונים see 2 Kings 23:17; Ezekiel 39:15. That תמרורים cannot mean “bitternesses,” as rendered by the Vulg. and the Targ., is evident from the verb that precedes it, which means to place, to set, to fix. תמר is the palm-tree; the word then means palm-tree pillars, or pillars straight and high as the palm-tree. The remainder of the verse is as follows, —
   Set thy heart on the highway, The way thou didst go;
Return, O virgin of Israel, return, To thy cities ascend.
   The word for “highway” means a raised road, a road prepared for travelling. The “virgin” here signifies one that is of an age to be married. When Israel repented, they were in a fit state to be united to God, as their husband. The last line is rendered according to the proposed emendation of Houbigant and approved by Horsley, עלה instead of, אלה which seems to have no meaning. — Ed

He then says, Apply thy heart — he now explains himself — apply thy heart to the footpath, to the way through which thou hast passed We thus see that the Prophet becomes the interpreter of his own words, even that the people would return along the same road, though they expected no such thing. And he again confirms the same declaration in other words, Return, thou daughter of Israel, return to thine own cities; as though he had said, “Though the land has beea deserted for a time, and reduced to solitude, yet the cities remain, which shall again receive their inhabitants; and through the wonderful favor of God the land still waits for its people.” Though it cast them out for a time, yet the exile was not to be perpetual, for the cities which remained were still by right the property of the people, not because they were worthy of them, but because God had prefixed, as it has elsewhere appeared, a set time for their exile and punishment.