“Gimmel De-Selichot” is the third day of reading Selichot (prayers for Divine forgiveness) according to Ashkenaz custom (quick reminder: this year the first day of Selichot was on the 22th of Elul).
In one of his letters (13 Elul 5710) the Rebbe writes that the uniqueness of this day was kept secret by Chabad leaders. On this day, they used to say a Chassidic discourse (maamar) – but only to their successors. However, the Rebbe Rayatz in his maamar finally revealed the merit of this day to all.
Even so, the full explanation of this day’s uniqueness did not become apparent. It is clear that the day is special, but why? The Rebbe explains that in our generation anyone can try to find the explanation on his own.
“… Even though one has to be careful in saying new pirushim (interpretations) and ramazim (clues), because not everyone is qualified for this, there are well-known words of our teacher (כ”ק אדמו”ר נ”ע) concerning interpretations in the Book of Tania: one should be careful with this, but if it brings an addition in avodah (Divine service) – he is allowed to say interpretations (and this was a message for all chassidim, not only for outstanding scholars). The same is true in regards to any matter: if it leads to the strengthening of avodah, Love of haShem and Fear of haShem, – it is permissible to say new interpretations and clues.
Getting back to our subject: “three” is a meaningful number. Even Matan Torah, the receiving of the Torah, is related to number three, as is said (Shabbat 88a): “Blessed is the all-Merciful One, Who gave the three-fold Torah (Torah, Prophets, and Writings), to the three-fold nation (Priests, Levites, and Israelites) in the third month (Sivan)”. The special power of the third day of Selichot is related to this – to the power of the third.
There are more connections between “Gimmel De-Selichot” and number three.
a) “Gimmel De-Selichot” always falls on the third day of the week (since the first Selichot service is held after “the day of rest” – Shabbat). The third day represents the third day of Creation – the only day in which the expression “ki tov” (“that it was good”) is mentioned twice. During the whole year the third day (both the day and the night) is considered a very special time of the week. And even more so – when the merit of “Gimmel De-Selichot” is added to the merit of the third day.
b) The whole idea of Selichot (forgiveness) is related to the third time Moshe Rabeinu ascended Mount Sinai and stayed there for 40 days, at which time haShem said to him: “Salachti Ki-Dvarecha – “I have forgiven [them] in accordance with your word” (Bamidbar, 14:20).
c) There are three expressions which convey forgiveness: “Selichah,” “Mechilah,” and “Kapparah”.
And there is more to add here, as is said (Mishley, 9:9): “Give a wise man, and he will become yet wiser”. (See more in the Rebbe’s talk on the third day of Selichot, 5748).
The Rebbe recommended to hold a chassidic gathering (itvaadut) on the “Gimmel De-Selichot” and to study at least a part of any Chassidic discourse related to this day (according to the personal choice of the learner).