בּוֹנֵ֣ה יְרוּשָׁלִַ֣ם יְהוָ֑ה נִדְחֵ֖י יִשְׂרָאֵ֣ל יְכַנֵּֽס׃
גאָט בױט ירושלים, די פֿאַרשטױסענע פֿון ישׂראל װעט ער אײַנזאַמלען;
Ibn Ezra
The word strays is a verb in the nif‘al form. The qal form of the verb can be seen in “He gathers together the outcasts of Israel” [Psalms 147: 2].
Ezra ben Solomon
Those who first went forth into exile will be the first to return. Some time later, the children of Judah will return. So Isaiah prophesied when he said: “In that day my Lord will apply His hand a second time to redeem the other part of His people from Assyria—as also from Egypt, Pathos, Nubia, Elam, Shinar, Hamath, and the coastlands” [Isa. 11:11]. The verse specifies “a second time,” for the redemption of the ten tribes will come first. And thus “the other part of His people” who will have remained in Assyria. In the following verse Isaiah lists the two exiles and makes mention of the two acts of redemption, referring to each and every one with its proper name. He says: “He will hold up a signal to the nations and assemble the banished of Israel; and gather the dispersed of Judah from the four corners of the earth” [Isa. 11:12]. He refers to the ten tribes as the “banished of Israel” as they dwell together but are banished from their land. The exile of Judah is designated as a dispersion, “and he will gather the dispersed of Judah.” The house of Israel will anoint a Messiah called Messiah ben Joseph; he will conquer lands and kingdoms and go to Jerusalem and rebuild it, as it is written: “The Lord builds Jerusalem, He gathers in the dispersed of Israel” [Ps. 147:2]. But he will die in battle. Of him it states: “In that day, the wailing in Jerusalem shall be great” [Zach. 12:11] and “they shall lament to Me about those who are slain” [Zach. 12:10]. Afterwards, the dispersed and scattered among the nations shall come and appoint a single leader, the Messiah, son of David, who was with them in exile. They will come to the Land of Israel with the permission of the kings of the nations and with their assistance. As it is written: “And out of all of the nations, said the Lord, they shall bring all your brothers on horses, in chariots and drays, on mules and dromedaries to Jerusalem, My holy mountain, as an offering to the Lord” [Isa. 66:20]. This kingdom will continue and never end. This is the meaning of “Thus declares the Lord God, Who gathers the banished of Israel” [Isa. 56:8]: these are the ten tribes. “I will gather still more to those already gathered” [ibid.]: I add yet another gathering to the first, the dispersed of Judah. This is the meaning of “The Lord your God will restore your exile and have mercy upon you. He will return and gather you from among all the nations among whom He scattered you” [Deut. 30:3]. It is possible that there may be a substantial period of time between these two ingatherings. Afterwards they might yet have to be as herdsmen in the wilderness of the nations, in order to separate out and purify the wicked among Israel, and to smelt them just as silver is smelt in the refining furnace, as happened during the Exodus from Egypt….208An eschatological discussion of Zech. 9:9 etc. has been ellipted.
Kli Yakar
And he was building a city. It doesn’t say “and he built” but rather he was building in the present tense, to indicate that he was continuously building all his days and his building was never completed. For this is their foolish way — that anyone who loves earthly possessions like Cain and his companions is forever building and proceeding, and can never complete his building all his days, because he never has enough of what he lacks. If he has one hundred, he desires two hundred, as is well known about the nature of all those who love money. Therefore, he is forever building and going, and all his days he has no rest, but rather is restless and wandering on the earth like Cain who was restless and wandering. So too is every lover of money — restless and wandering, sitting at home little, as most of his days he chases after wealth as if he were hunting a partridge in the hills. He runs with feet like deer through the desert, mountain, and lowland, crossing ocean paths, all the days of his life — these being the nights too, as even at night his heart does not rest. For he will go to all dangerous places to attain what his soul loves; they will seek but not find, and will never reach their goal, rather all their days they are building and going — cities of poverty that endanger their soul and body, leaving for others the wealth and walls which they built and planted. And a sign for this matter: In the alphabet, the letters spelling “poor” are adjacent and follow the letters spelling “money,” indicating that all who love money are forever poor in their mindset. But that which is said The Lord builds Jerusalem (Psalms 147:2) in the present tense can be explained according to what is concluded in the Gemara (Bava Batra 75a): He saw ministering angels who were cutting precious stones and pearls, etc. He said to them, “For whom are these?” They said to him, “The Holy One, Blessed be He, will set them in the gates of Jerusalem, etc.” If so, at all times The Lord builds Jerusalem, and this is easily understood. Similarly, the language of “building” said regarding Cain hints that he was continuously building forever, as it is written A man to whom God will give wealth and possessions, etc., but God will not enable him to eat from it (Ecclesiastes 6:2). Note that “will give” is in the future tense, when it should have said “gave.” Rather, this is its interpretation: Anyone who is not satisfied with what God has granted him and is always seeking what God will give him — more wealth and possessions beyond what he already has — such a person is surely a scoundrel, a miser, and a penny-pincher, and has no control over his own possessions to eat from them, all the more so to give to others.