Saying Parshas HaMun:[1]

Its proper[2] for one to recite daily[3] the paragraph of the Mun [heavenly bread] in order to strengthen ones trust [i.e. Bitachon] in G-d who provides ones food on a daily basis.[4] Alternatively, it is recited in order to strengthen one’s belief [i.e. Emuna] that all of one’s food comes to him with Divine providence[5], as G-d decided to give one portion of Mun per family, and those who took more, had their portion decrease to the allotted portion, while those who took less had their portion increase to the allotted portion.[6] [Thus we see that whatever G-d decides to give a person is what he will get no matter if he tries to get more or less.]

^[1] Admur Kama 1:10, Basra 1:9; Michaber 1:5; Tur 1:5; Sefer Hamanhig Shabbos 44; Tashbeitz Dinei Tefila 256; See Piskeiy Teshuvos 1:16; Likkutei Sichos Vol. 26 pp. 111-120 in length for the differences between the first and second version of Admur

^[2] Lit. “Tove”

[3] Regarding saying it on Shabbos: Some write that it is to be said even on Shabbos. [Beir Heiytiv 1:9; Implication of Sefer Hamanhig Shabbos 44; Likkutei Sichos ibid according to Kama ibid] See Likkutei Sichos ibid p. 114 that according to reason of Basra ibid it may not be said on Shabbos as its Bakashas Tzerachav

^[4] Admur Basra 1:9; Taz 1:4; See Likkutei Sichos ibid

[5] Admur Basra 1:9; Taz 1:4; Beis Yosef 1; See Likkutei Sichos ibid

^[6] Admur Kama 1:10; Levush

[7] Piskeiy Teshuvos 1:16 based on Arizal in Hakdama Shaar Hakavanos; Maharam Rikanti in Taamei Hamitzvos; Yifei Laleiv 1:24; Orchos Chaim Spinka 1:7

The reason: This is based on the teachings of the Zohar which states that one should not make a request for his own needs prior to prayer. [Zohar Pinchas p. 226]

[8] See Mishmeres Shalom 14:2; Piskeiy Teshuvos 132:14

[9] See Igros Kodesh 12:18, printed in Shulchan Menachem 1:281; In the siddur this paragraph is not brought by Admur and is thus not accustomed to be said by Chabad Chassidim.

[10] Yerushlami Brachos [in unknown page]; Perisha 1; M”B 1:6; See Likkutei Sichos ibid footnote 2

[11] Igros Kodesh 12:18