The most appropriate time to study during the day – after Shacharis:[1] It is a Mitzvah Min Hamuvchar to establish the required set time of daytime Torah study for immediately after Shacharis, prior to going to work. Whoever leaves the synagogue and goes directly to the house of study  in order to study Torah, merits to receive the face of the divine presence, as the verse[2] states “Yeilchu Meichayil El Chayil Yirah El Elokim Betziyon.” Nevertheless, one who is accustomed to eating Pas Shacharis [i.e. breakfast], may eat it as soon as he leaves from Shul after Shacharis, even prior to going to the Beis Hamidrash to learn after Davening.[3] [However, some write that it is not proper to eat breakfast prior to one’s set learning session after Shacharis.[4] Practically, this only refers to eating a set meal, however a small breakfast of a Kezayis or Kebeitza of Mezonos in order to not leave one’s stomach empty, is proper to be eaten before learning.[5]]

Not to override one’s set Torah study times even to make a lot of money:[6] The set time that one who works establishes for his daily Torah learning, as stated above, must be set in a way that it is not nullified even for the sake of making a large profit.[7] [Such an individual is considered a man of faith, who believes and trusts in G-d that his Torah study will not cause him a loss in income,] as he tells himself that if G-d wills him to make a profit he will make it regardless, even if he delays his work until after his learning.[8]] However, in the event that one needs to deal with a pressing matter during his time of learning, then he may [push it off and] make up the learning later on that day or in the evening.[9] Nonetheless, even in such a case, it is proper for him to learn at least one Halacha or one verse immediately after Shacharis.[10]

Saying Beli Neder:[11] If one accepted upon himself to learn a certain matter then it is considered a vow [unless he explicitly stated “Beli Neder”]. One is thus to initially state “Beli Neder” upon taking a new Shiur or learning schedule upon himself.[12]

[1] Admur 155:1; Michaber 155:1; Tur 155; Rabbienu Yona in Sefer Hayirah; Emak Habracha 2:42; Yeish Nochalin Inyan Tlamud Torah; Brachos 64a; Moed Katan 29a; Midrash Raba Shemos 2; Yerushalmi Shevi’is 4; Targum Yonason on Tehillim 84:8; See Likkutei Sichos 7:50; Toras Menachem 23:220; Igros Kodesh 10:102; See Piskeiy Teshuvos 155:1

[2] Tehillim 84:8

[3] Admur 155:1; Tur 155; Levush 155:2; Bava Kama 92b; Bava Metzia 107b; M”B 155:11; Kaf Hachaim 155:22

The reason: The reason for why eating breakfast is so important is because there are 83 illnesses, which is the numerical value of the word “מחלה”, which are dependent on the gallbladder, and all of these illnesses can be avoided by eating bread with salt and drinking a jug of water in the morning. [Admur ibid]

[4] Reishis Chochma Shaar Hakedusha chapter 15; Seder Hayom writes to learn Torah right away after Davening and only to eat in between if he is weak and plans to learn for many hours and cannot concentrate if he doesn’t eat; Zohar Kadosh Beshalach 62b; Piskeiy Teshuvos 155:1 and 8 footnote 3

[5] Kaf Hachaim 155:23

[6] See Admur 155:1-2; Hilchos Talmud Torah 3:4; See Piskeiy Teshuvos 155:1

[7] Admur 155:1; Michaber 155:1; Tur 155:1; M”B 156:4

[8] M”B 155:5; Yerushalmi Sotah 89b

[9] Admur 155:2; M”A 155:1; M”B 156:4; Rav Acha Bar Yaakov in Eiruvin 65b; Emek Habrcha 2:42; See Michaber 238:2; Yeish Nochlin Inyan Talmud Torah

Contradiction: This ruling seemingly contradicts the previous ruling brought in the previous sentence which states that one should never nullify his set time of Torah learning even to make a large profit. Indeed, the M”B ibid. when he records this ruling does not state that one may push off his set time of Torah learning in a pressing situation, but rather simply that if due to reasons beyond his control he couldn’t learn during the daytime, then he should make it up at night time. Practically, however, it seems the following is the explanation: To nullify the daytime Torah study for that entire day, and not even make it up at night, is never allowed even to make a lot of money, unless it is due to reasons completely beyond his control. However, to simply change the time and make it up at a later time or earlier time during the day is permitted in a pressing situation. Vetzaruch Iyun. See Piskeiy Teshuvos 155:5; See also Admur Hilchos Talmud Torah 3:4 that he he may shorten his learning session for Parnasa reasons

[10] Admur ibid; M”A ibid; M”B ibid; Emek Habracha ibid; See Avos 6:3; Piskeiy Teshuvos 155:5; See Admur Hilchos Talmud Torah 3:4 that in time of need for single making a living, he may shorten his learning session to learning one chapter at day and one chapter at night, and in a very present situation he may rely even simply reading the Shema by day and night

[11] Michaber Y.D. 213:2; 203:4; 204:6; Shach 204:5; M”B O.C. 238:5 in name of M”A; Nedarim 8a; Piskeiy Teshuvos 155:5

[12] M”B ibid