Welcome to Embrace Shabbat.
Gemara Shabbat (119b) says that for one who prays on Erev Shabbat and recites “וַיְכוּלּוּ,” two angles accompany him, place their hands on his head, and say to him: וְסָר עֲוֹנֶךָ וְחַטָּאתְךָ תְּכֻפָּר, your sins will be removed and your unintentional sins have been atoned. What is it about accepting Shabbat and saying Kiddush that brings this kapara?
The Maharsha explains that when a person recites Kiddush, they become a partner with G-d in creation. This invokes the power of that time in history: Adam HaRishon was forgiven for his sin at the same moment of knisat Shabbat. Just as Yom Kippur is a time of kaparah because it is when the Jewish people were forgiven for the sin of the Golden Calf in history, Erev Shabbat is a time of kaparah, as it was when Adam HaRishon was forgiven for his sin.
The Chidah offers another explanation. When a person recites Kiddush, they testify that G-d created the world. In Jewish law, a person must be a kosher witness before testifying in court. Therefore, when a person testifies about the creation of the world in Kiddush, G-d forgives his sins so that he can be a kosher witness.
The Ben Ish Chai brings another interesting explanation. A person must light at least two candles on Friday night. On a simple level, these two candles correspond to זכור and שמור, the positive and negative commandments on Shabbat. Additionally, the candles correspond to a husband and wife, who also represent positive and negative, because one is a giver and one is a receiver. On Erev Shabbat, the husband and wife become unified and are considered one body. A man has 248 organs, and a woman, because of her reproductive system, has 252 organs. Combined, the husband and wife have 500 organs, which is the numerical value of two candles (נר = 250). This is one of the reasons that it says that Shemirat Shabbat is k’neged all of the mitzvot of the Torah; the light of Shabbat enlightens all of the limbs of a person’s body.
חנון המרבה לסלוח, G-d is gracious and He is abundant in His forgiveness, also has the same numerical value of 500. This is another source for this surge of forgiveness that happens on Erev Shabbat. Lighting Shabbat candles is a tikkun for the sin of Chava, after which the two angels come down and bring kapara to the world.
This is the source for those who go to the mikvah on Erev Shabbat. Just as there is a minhag to go to the mikvah on Erev Yom Kippur because it is a time of kaparah, people go to the mikvah on Erev Shabbat. A time of kaparah must be accompanied by introspection and teshuva; it does not happen automatically.
The Sefer Iyun Yaakov says this hirhur teshuva is almost built into the Kiddush process. When a person realizes that HaKadosh Baruch Hu created the world and is in charge of everything, they immediately regret anything that they did wrong.
Finally, Erev Shabbat is a time for kaparah because it is when we testify to the fact that G-d created the world. The concept of forgiveness seemingly doesn’t make any sense. A court cannot just forgive a person’s sins! The man sinned, so they get punished. מלך שמחל על כבודו אין כבודו מחול, a king cannot forgo their honor. So how is HaKadosh Baruch Hu able to forgive?
The Gemara (Kiddushin 32a) explains that HaKadosh Baruch Hu controls the world and therefore can do whatever He wants; He doesn’t have to follow the rules of the world. But this can only be true if a person believes that HaKadosh Baruch Hu runs the world and is in charge of everything. When a person says Kiddush on Friday night and testifies that G-d created the world and controls everything, it “empowers” G-d to forgive them.
Let us all take advantage of all of the reasons for Shabbat bringing a kaparah, recognizing all of the great powers that Erev Shabbat has to forgive.
Have a wonderful day and Shabbat Shalom.