מוסר אויף ירמיהו 31:15

Mourning - Mourning over the destruction of the Beit Hamikdash [the Temple] is something that depends on action, and especially during the period of the Three Weeks, by day and night [one should] place ashes on the place where the Tefillin are laid, sit beside the Mezuzah, and recite the order of the Tikkun Chatzot. In truth, the action is not the core [of mourning], rather one must have an eye that weeps bitterly and a broken and crushed heart — like one mourning for his mother, gloomy, he should sigh with “brokenness of the loins” [i.e. being crushed by grief] over the sorrow of Heaven. And all is proportional to one’s knowledge, greatness of love [of Heaven], and the reward of his soul. And see the truth is that we are greatly diminished, and there is no one among us who knows what we are lacking, what we have lost, what we have caused through our many sins, what the exile of the Shekhinah is like, and [the extent of] the suffering of the upper and lower beings. Over this, all who are sorrowful should grieve, [but] in any case every man isn’t obligated except according to his [own] capacity. And he should imagine as though his mother were girded with sackcloth, wearing black [garments] and wrapping herself in black [garments], crying out bitterly — a voice heard in Ramah [on high, but see Jeremiah 31:15 snd other verses] — moaning like a dove. What does the language say? (Sanhedrin 46a): “I am distressed about my head, I am distressed about my arm”. “I have reared and brought up children, and they have rebelled against me” (Isaiah 1:2). And like this and that the living should take to heart things that embitter the heart. He should pour out his soul with a wailing voice; perhaps he will merit to see the consolation of Zion and the rebuilding of our Temple and our glory, that it be speedily rebuilt in our days, Amen.

After having seen the ladder in his dream, Jacob understood a number of things; among them he understood the meaning of the four exiles he had seen in his vision, and he understood the eventual redemption. This is why he said: "Indeed G–d is in this place, אכן יש ה' במקום הזה, but I did not know it." He expressed his new found-understanding that the third Temple would lead to the realization of הזה and יש. He realized that this והתהלכתי בתוככם would be fulfilled במקום הזה. These two realizations all resulted from the וישכב, when he lay down to sleep. Concerning this experience we find an allusion in Jeremiah 31,16: יש שכר לפעולתך, "there is a reward for your labor." An example of the reward for וישכב, is the incident of Leah having traded the mandrakes her son Reuben had found in order to have an extra night with Jacob. Rachel had agreed with the words : לכן ישכב עמך, "therefore he may lie with you." When Leah became pregnant as a result of that night, and Issachar who founded the tribe that excelled in Torah study was born, she stated: נתן אלוקים שכרי, "G–d has given my reward." It was Issachar who would excel in bringing about the period described as ומלאה הארץ דעה, that the earth would become full of knowledge (of G–d).