Midrash su Salmi 137:5

“I called to my lovers, they deceived me; my priests and my elders perished in the city while they sought food for themselves to restore their souls” (Lamentations 1:19).
“I called to my lovers, they deceived me.” The Rabbis interpreted the verse regarding false prophets, who would cause their idol worship to be beloved to me.²⁰⁵The rabbis interpret the term me’ahavai, generally translated “my lovers” to mean “those who made [idols] beloved to me.” The verse is written from the perspective of Zion. “They deceived me,” they, too, deceived me. They did not cease prophesying falsely about me until they caused me to be exiled from my place, as it is stated: “They envisioned for you prophecies of futility and deviance [umaduḥim]” (Lamentations 2:14); it is written madiḥam.²⁰⁶The word maduḥim is written without a yod, such that it can be read madiḥam, meaning those who have pushed them into exile.
Rabbi Shimon bar Yoḥai interpreted the verse regarding the true prophets, who would cause me to be beloved to the Holy One blessed be He. “They deceived me,” as they would deceive me and say to me: Separate teruma and tithes. But are there teruma and tithes in Babylon? Rather, it was in order to cause me to be beloved to the Holy One blessed be He. That is what Jeremiah says: “Establish signposts [tziyunim] for you” (Jeremiah 31:20). Distinguish yourself via mitzvot with which Israel was distinguished.²⁰⁷Therefore, separate teruma and tithes even in Babylon despite the fact that these mitzvot apply by Torah law only in the Land of Israel.
“Place landmarks for you” (Jeremiah 31:20), this is the destruction of the Temple.²⁰⁸A landmark serves as a marker or reminder of something. This is understood as an allusion to the destruction of the Temple, which must be remembered. Likewise it says: “If I forget you, Jerusalem, let my right hand lose its power” (Psalms 137:5). “Note the highway, the path that you walked [halakht]” (Jeremiah 31:20). Rabbi Ḥiyya said: “I walked [halakhti]” is written.²⁰⁹The verse in Jeremiah is written “the path that I walked,” but it is traditionally read as though it says “the path that you walked.” You find that when Israel was exiled to Babylon, what is written? “For your sake, I sent to Babylon” (Isaiah 43:14).²¹⁰The midrash interprets this to mean that God sent His own Divine Presence with them into exile. Alternatively, the term “I sent [shilaḥti]” can be read shulaḥti, meaning I was sent. They were exiled to Eilam; the Divine Presence was with them, as it is written: “I will place My throne in Eilam” (Jeremiah 49:38). They were exiled to Greece; the Divine Presence was with them, as it is written: “I will rouse your children, Zion, against your children, Greece” (Zechariah 9:13), and it is written thereafter: “The Lord will appear over them…” (Zechariah 9:14). That is why it is written: “The path that I walked.”
Another matter, “Note the highway, the path that you walked.” Jeremiah said to them: ‘See the paths on which you have walked, and repent, as it is written: “Return, maiden of Israel” (Jeremiah 31:20), and you will immediately return to your cities, as it is written: “Return to these, your cities” (Jeremiah 31:20).

(Fol. 61b) Our Rabbis were taught: After the destruction of the second Temple many abstemious persons who refused to eat meat or drink wine were increased in Israel. And R. Joshua approached them, saying: "My children, why do you not eat meat and do not drink wine?" They replied: "How should we eat meat of which sacrifices were brought, or drink wine which was offered at the altar?" R. Joshua said to them: "If so, let us not eat bread, as the meal-offering is also abolished, for we can live on fruit?" Whereupon they replied: "Fruit was also [used in the Temple as] the first fruit offering." But then let us eat only such fruits of which no Bikurim was brought? And again let us abstain from drinking water, since the custom to put water on the altar no longer exists?" And they were silent. Then said R. Joshua to them: "My children, come and listen to me. It would be wrong not to mourn at all, since it has already been decreed to mourn. But to mourn too much is also impossible, for we must not impose a restriction upon the public unless the majority of the public can endure it." R. Ada b. Ababa said: "Where is the passage to prove this?" It is written (Mai. 3, 9) With a curse to be cursed [have ye obligated yourselves to give tithes] and yet Me you rob, O ye entire nation, i.e., if the entire nation [accepted the curse] then it could be extended, but not for a part of it. Therefore, the sages said: "When one paints his house, he shall leave a little spot unpainted as a sign of mourning." How much? Rab Joseph said: "A square yard." R. Chisda added: "This should be opposite the door." One may prepare all that he needs for his meal, leaving out some little things as a sign of mourning. And the same is the case with a woman. She may dress herself with all her ornaments, leaving out some of the unimportant for that purpose, as it is said (Ps. 137, 5) If I forget thee, O Jerusalem, may my right hand forget. May my tongue cleave to my palate if I do not remember thee; if I recall not Jerusalem at the head of my joy." R. Isaac said: "This refers to the calcined ashes [which it is customary to put on the head of the groom] on the day of his marriage." R. Papa asked Abaye: "Where do they place it?" He replied: "They used to place it on their foreheads at the place of the phylacteries, as it is said (Ls. 6, 13) To grant unto the mourners of Zion to give unto them ornament in the place of ashes. And every one who is mourning for Jerusalem will be rewarded by seeing her joy. As it is said (Ib. 66, 10) Be highly glad with her, all ye that mourn for her."

... R’ Yitzchak expounded on, “On willows in its midst we hung our harps.” (Psalms 137:2) Come and see – the dirt of the land of Israel is for repentance. While they were still in the land of Israel, Jeremiah was saying to them ‘repent before the judgement is sealed upon you,’ and they did not accept his words. Once they were exiled, they kept themselves sanctified through the commandments, taking their harps and hanging them on the willows. “For there our captors asked us for words of song…” (Psalms 137:3) At that time the nations of the world said to them: stand up and sing before idols just as you would sing in the Holy Temple. They replied: if we had sung songs in our place, we would not have been exiles. And now how should we sing songs before idols?! R ‘ Yitzchak Tavlai would say: to what is this to be compared? To a king of flesh and blood who married the daughter of kings. He said to her: get up and bring me a cup to drink, and she did not want to serve him. He was angry with her and drove her from his house, and she went and married a man who was afflicted with boils. He said: get up and bring me a cup to drink. She said to him: worthless one! I was a daughter of kings, married to a king, and because he said ‘bring me a drink’ and I did not want to serve him he was angry with me and drove me from his home. In that case if I had served him I would have added to my honor and had honor in my place, and now you say to me get up and serve me?! So Israel says to the nations of the world: if we had sang songs before the Holy One in our place on all the miracles which He did for us, we would have stayed in our place and not been exiled from our land. Now we should sing songs before idols?! Immediately they arose and killed heaps and heaps of them, and even though many of them were killed Israel rejoiced that they did not sing songs before the idols, as it says “…and our tormentors [asked of us] mirth…” (ibid.) At that moment the Holy One swore a whole oath to Israel. He said of Himself, so to speak, if I do not keep my oath, as it says “If I forget you, O Jerusalem, may my right hand forget [its skill].” (Psalms 137:5) The Holy One took His hand and placed it behind Him at the moment when Israel was exiled, just as it says “He has withdrawn His right hand from the enemy…” (Lamentations 2:3) The Holy One, so to speak, did not return it to its place. And so too the Holy One said to Israel: I will forget My right hand which I placed behind Me if I do not fulfill my oath to you and not forget you among the nations. “May my tongue cling to my palate, if I do not remember you, if I do not bring up Jerusalem at the beginning of my joy.” (Psalms 137:6) In the future the Holy One will return to Jerusalem all of her joy, as it says “And the redeemed of Zion shall return, and they shall come to Zion with song, with joy of days of yore shall be upon their heads…” (Isaiah 35:10) And anyone who mourns for Jerusalem in this world will rejoice with her in the time to come, as it says “Rejoice with Jerusalem and exult in her all those who love her: rejoice with her a rejoicing, all who mourn over her.” (Isaiah 66:10) They said in the name of Abaye: joy only comes on the ninth of Av, because they mandated mourning then in this time and in the future the Holy One will make it into a holiday, as it says “…and I will turn their mourning into joy and will comfort them and make them rejoice from their sorrow.” (Jeremiah 31:12) ... “No one pitches my tent anymore, or sets up my curtains.” (Jeremiah 10:20) What is this, does it mean that the Holy Temple will not be rebuilt in the future?! No, rather it is saying that no one from among you will pitch my tent anymore nor anyone from among you shall set up my curtains. The First Temple, which was built by flesh and blood, fell at the hands of the enemy. But the final Sanctuary that will be built by the Holy One, as it says “The Lord is the builder of Jerusalem; He will gather the outcasts of Israel,” (Psalms 147:2) will not be destroyed. Therefore it says “My tent has been spoiled…” (Jeremiah 10:20)