The Meor Einayim (Mikeitz) writes, "Hashem gave Shabbos to the Jewish nation so we can be close to Him. When one keeps Shabbos, all his sins are forgiven. However, it is hard to tap into the holiness of Shabbos because the holiness of Shabbos is so extremely exalted. שבת is Hashem's name; how can a person ascend to this high, exalted place? On Chanukah, Hakadosh Baruch Hu, keviyachol, goes down lower than ten tefachim [to the people at very low levels] and draws them up so they too can experience Shabbos. This is the explanation of שאין פתילות בחנוכה בהן מדליקין בשבת מדליקין , 'Wicks that one can't use on Shabbos, one may light with them on Chanukah.' The wicks represent people, בשבת מדליקין שאין, who don’t become illuminated on Shabbos, בחנוכה בהן מדליקין, they can become illuminated on Chanukah. Hashem, Himself, keviyachol, lowers Himself down to the person and kindles his neshamah." So, Shabbos Chanukah is an exceptional opportunity. If we have trouble connecting to Hashem on Shabbos, we have the potential to succeed in binding with Hashem on this Shabbos.
Rebbe Yisrael of Ruzhin zy'a would repeat in the name of his father, Rebbe Shalom Shachnah of Pravitch zy'a, that the Shabbosim until Chanukah are alluded to in the words, "The earth was ובהו תהו, empty and void." Even the Shabbosim lack their shine and brilliance. But when Chanukah comes, it states, אור יהי אלקים ויאמר, "Hashem said, there should be light," as from then on, one can more easily attach himself to the holiness of Shabbos.
