Chasidut for Kiddushin 59:10
לעולם ישלש אדם שנותיו שליש במקרא שליש במשנה שליש בתלמוד מי יודע כמה חיי לא צריכא ליומי
because they used to count all the letters of the Torah.<span class="x" onmousemove="('comment',' To safeguard the correctness of the text. Soferim is taken in the original sense of its root safar, 'to count'.');"><sup>19</sup></span> Thus, they said, the waw in gahon<span class="x" onmousemove="('comment',' Whatsoever goeth upon the belly (iujd) - Lev. XI, 42.');"><sup>20</sup></span> marks half the letters of the Torah; darosh darash,<span class="x" onmousemove="('comment',' Lev. X, 16: And Moses diligently enquired after - darosh darash - the goat of the sin-offering.');"><sup>21</sup></span> half the words; we-hithggalah,<span class="x" onmousemove="('comment',' Lev. XIII, 33: we-hithggalah, then he shall be shaven. [In M.T. the words 'he placed on him' (Lev. VIII, 8) is given as the middle verse.]');"><sup>22</sup></span>
Kedushat Levi
Besides, how could Joseph arrogate to himself the right to give such instructions, when we have it on the authority of Kidushin 30 that a person should strive to divide the activities he performs (equally) into the three parts of his life, devoting one third to the study of the written part of the Torah, another to the study of the oral part of the Torah, (Mishnah) and the third part to the discussions on the oral part of the Torah in the Talmud. One difficulty of that statement is that we do not know how long we are going to live, so how can we make the correct division? The Talmud therefore corrects itself, saying that what is meant is the way we divide each day of our lives. It follows that each one of us is duty bound to study some halachah on a daily basis. So how could Joseph forbid this to his brothers?
The statement in the Talmud can be seen as plausible if we first consider two premises upon which it is built. 1) Yaakov had a tradition that he need not fear ever being consigned to gehinom provided that none of his children died during his lifetime. (Rashi 37,35 based on a Tanchuma Vayigash 9. 2). A statement by our sages that the combined lifetimes of the patriarchs would be 500 years, corresponding to כימי השמים על הארץ, (Deut.11,21). [According to a number of commentators this verse describes the “distance” between earth and the celestial regions through the intervening רקיע, outer space, being equivalent to 502 “years.” The combined lifetimes of the patriarchs, were 502 years, though more than half of these overlapped, and we do not know the criteria applied here, i.e. “light years,” i.e. the time it takes light to traverse this distance, or whatever other criteria are referred to. Ed.]
If a human being were to know how long he was going to live on this earth, he would be able to apportion one third of his life to the respective study of Torah, Mishnah, and Gemara. Based on the above calculation, when Yaakov saw that Joseph had disappeared, he concluded that he must be dead, so that one of the premises, i.e. that he would not have to worry about spending time in gehinom had already lost its comforting meaning. From that moment on he became afraid that the second premise we have mentioned could also be compromised, as he had no idea how long he would live. He was therefore unable to instruct his sons to leave out the study of halachah, i.e. gemara, for a single day. Joseph, who was aware that his father had no reason to worry, as all his sons were alive and well, was able to issue such a command without endangering the spiritual future of his father. The brothers would have lots of time to make up for the halachot they had not studied while on the journey to bring good news to their father.