Musar su Salmi 126:1

In the Zohar on Parashat Terumah [it is taught]: 'One who luxuriates at his table and delights in those foods ought to call to mind and to feel concern for the holiness of the Holy Land and for the Temple of the King that has been destroyed. In consideration of the sadness that one feels at one's table--in the midst of the joy and celebration [lit. drinking] there--the Holy Blessed One accounts it to one as if one has rebuilt His House and rebuilt all the ruins of the Temple. Happy is one's portion!' (Zohar 2:157:2). Therefore it is customary to recite the Psalm 'By the waters of Babylon' (Psalms 137) before Grace after Meals, particularly since the table corresponds to the (Temple) altar, while, through our many sins, the altar itself is no longer. One should call to mind [the teaching], 'Woe to the children who have been banished from their Father's table' (Talmud Berachot 3a). The banishment from the Table (shulchan, sh.l.h.n) was caused by the power of the Snake (lenachash, l.n.h.sh), as is taught in the Zohar [about the word] Eichah ('.y.kh.h, 'Alas;' the name of the Book of Lamentations): 'I shall set enmity' (Eivah, '.y.b.h) (Genesis 3:15), an anagram for א׳יכה י׳שבה ב׳דד ה׳עיר 'Alas, the city sits solitary' ('.y.b.h) (Lamentations 1:1). On Shabbat and Festivals one recites the Psalm 'When the Name restores the fortunes of Zion' (Psalms 126).