- The Background & History:
The word Chitas stands for Chumash, Tehillim, Tanya. Its daily learning was established by the Rebbe Rayatz. The daily learning allotments were first published in the Sefer Hayom Yom, in the year 5703, as requested by the Rebbe Rayatz to the Rebbe. Its Segula was initially revealed 100 years earlier, in the year 5603/1843, to the Tzemach Tzedek by his mother Rebbetzin Devorah Leah, who in turn was informed of its importance by the Baal Shem Tov, as explained next
The first known significance of the combination of Chumash Tehillim and Tanya: Rebbetzin Devorah Leah told her son the Tzemach Tzedek that the Baal Shem Tov informed her that since he is expert in the words of Chumash, Tehillim, and Tanya, therefore he will be successful in the Rabbinical conference that was held with the government officials that year, and manage to banish all of the concealments. The Tzemach Tzedek then later informed his son, the Rebbe Maharash, in the year 5617/1857 that he should recite from memory a paragraph of Chumash Tehillim and Tanya by each meeting with a government official. The Rebbe Maharash informed his son the Rebbe Rashab that with the recital of three paragraphs of Chumash, Tehillim, and Tanya, he managed to ruin all of the plans of the Maskilim.
The start of the Takana to study the daily Chumash with Rashi: While the custom of the recital of the daily Tehillim after Davening, and likewise the daily recital of a piece of Tanya is the novelty of the Rebbe Rayatz, the recital of the daily Chumash with Rashi is in fact a very old tradition dating back to the times of the Alter Rebbe [and perhaps earlier], having been established by him. The Rebbe Rayatz stated in the name of his grandfather, the Rebbe Maharash, that one is required to learn daily Chumash with Rashi. Nonetheless, it seems that this tradition did not take the full force adaption by Chassidei Chabad until it was published in the Sefer Hayom Yom. Accordingly, this Takana is likewise attributed to the Rebbe Rayatz.
The start of the Takana to recite the daily Tehillim after Davening: The Takana to recite the daily Tehillim after Davening was first established by the Rebbe Rayatz in the year 5687/1927. From that year and onwards, the Rebbe Rayatz would encourage the Chassidim in dozens of lectures and letters to take upon themselves this daily recital.
The start of the Takana to study the daily Tanya: The daily study of Tanya was seemingly first established in the year 5703 when the Sefer Hayom Yom was first published, and marked the first time that the daily study portions of Tanya were published. The allocation of each day’s portion was done personally by the Rebbe Rayatz for the upcoming publishing of the calendar of Hayom Yom.
 See Hiskashrus Nitzutzei Rebbe Vol. 167-217 p.69 in Otzer Hachochmah print; Shulchan Menachem Vol. 1:102; Likut of Rav Slonim in Chitas
 Sefer Hasichos Parshas Bereishis 5752 Vol. 1 p. 56
 Sefer Hasichos 5705 p. 97; Igros Kodesh Rayatz 7:30; Igros Kodesh 11:232; 13:425; 18:178
 See Igros Kodesh Rayatz 7:30; Introduction of Rebbe to Hayom Yom
 See Igros Kodesh Rayatz 4:268; Sefer Hasichos 5696 p. 158
 See Likut of Rav Slonim in name of Shibulei Haleket Inyan Tefila 44; Rashi Brachos 32b; Arizal in Shaar Hamitzvos Parshas Vaeschanon and Kaf Hachaim 132:6 that the Arizal would learn the weekly Parsha each day after Davening
 See Hayom Yom 19th Teves [includes Rashi]; Hayom Yom 2nd Cheshvan [although learning Rashi is not mentioned]; letter of 22nd Shevat 5718; Kuntrus Bikur Chicago Sicha 1; Sefer Hasichos 5702:27
 Hayom Yom 18th Adar Sheiyni
 See Hakdama of Hayom Yom Mevueres p. 17
 See Igros Kodesh 13:425
 See Igros Kodesh Rayatz 7:30