Midras Mazmur 147:2: Ein Yaakov (Glick Edition), Midrash Tanchuma, Pesikta DeRav Kahana & Mekhilta DeRabbi Shimon Ben Yochai

(Fol. 87) It is written (Is. 62, 6) I have set watchmen upon thy walls, O Jerusalem. They shall never be silent, day nor night. Ye that make the Lord's remembrances, take ye no rest. What did they say? Said Raba b. R. Shila (Ps. 102, 14) Thou wilt arise, and have compassion upon Zion; for it is time to be gracious unto her, for the appointed time is come. R. Nachman b. Isaac said: (Ib. 147, 2) The Lord does build up Jerusalem, He gathereth together the dispersed of Israel. And what did they say before [the destruction of the Temple]? Said Raba b. R. Shila: (Ib. 132, 13) For the Lord hath chosen Zion; He hath desired it for His habitation.

The Lord has sworn by His right hand and by the arm of His strength (Isa. 62:8). By his right hand refers to the Torah, as it is said: His right hand was a fiery law unto them (Deut. 33:2). And by the strength of His arms alludes to the tefillin (phylacteries), as it is said: The Lord will give strength unto His people (Ps. 29:11). Surely I will no more give thy corn to be food for thine enemies … in the courts of My sanctuary (Isa. 68:8–9) refers to Jerusalem. What oath did He proclaim in reference to Jerusalem? He vowed that He Himself would build it, as it is said: The Lord doth build up Jerusalem; He gathered together the dispersed of Israel (Ps. 147:2).

R. Samuel the son of Nahmani stated: There is an aggadic tradition which states that Jerusalem will not be rebuilt until the dispersed of Israel are gathered together. However, if one should tell you: The exiles are already gathered together and Jerusalem still hath not been rebuilt, believe him not, for it is written: The Lord doth build up Jerusalem, and after that Scripture says: He gathered together the dispersed of Israel (ibid. 147:2).