Kabbalas Hatorah in the Winter
Kislev, the third month of the winter, corresponds to Sivan, the third of the summer months. Now, Sivan is the month of Matan Torah; as our Sages state, “A threefold Torah, [comprised as it is of Torah, Nevi’im and Kesuvim] … given in the third month: [Sivan, the third month from Nissan, the ‘first of months’].”
Not only does Kislev parallel Sivan, but Kislev even holds superiority over Sivan. [For although the Torah was given in Sivan, nevertheless,] the actual service of Torah study is more pronounced … and further emphasized [in Kislev] to an even greater extent than the Torah study of [Sivan,] the third of the summer months.
Long nights – lengthy study
What is Kislev’s superiority over Sivan? It involves what the Tanya describes as “He who serves Hashem” [by going beyond his habitual limits within Torah study]: As winter progresses, the days become shorter and the nights grow longer; we therefore increase our current schedules of nightly Torah study; for our Sages state (Eiruvin 65a) that “the night was created only for the study of Torah.”
We further add to the quality of our study, by toiling in the in-depth study of Torah – the intricate expositions and analyses of the Sages. This kind of study is represented in the Hebrew word for “winter,” choref, which is related to charifus, “sharpness” [in learning]. (Parshas Vayeitzei 5751; Hisvaaduyos, p. 353)