[This Chapter] will Explain How One Causes Damage to himself Through this [sin of Lashon HaRa] in Respect to a Number of Matters
““Do not allow your mouth to bring sin upon your flesh…” – this refers to Lashon HaRa.
“…Why shall G-d be angry concerning your voice…?” – Concerning that voice which you emitted from your mouth in order to speak Lashon HaRa against your fellow.
“…and destroy the work of your hands.” – ["The work of your hands" refers to] the small [amount] of Torah that you possess “in your hands” [which is] lost [as a result of the sin of speaking Lashon HaRa].”
It is obvious [that the intended teaching] of the [above] Midrash follows that which is written in the holy books, [where we learn that] one who speaks Lashon HaRa against his fellow, personally causes that the merits of the speaker [of Lashon HaRa], gained up until this point are detracted from him and transferred to his fellow [who was the victim of his Lashon HaRa].
Furthermore, due to [the Lashon HaRa that he spoke], his prayers are not accepted Above, [in Heaven], as is written in the Holy Zohar, Parshas Mitzora: “The prayer of one who has committed the [sin of Lashon HaRa] does not rise before The Holy One, Blessed is He, for the Spirit of Impurity has aroused itself upon him. Once he returns [from committing this sin in the future through his] repentance [from his sin of Lashon HaRa] and has accepted upon himself to repent, [then] what is written in reference to him? “On the day that he becomes pure he shall be brought before the Kohen”… (Vayikra: 14; 2)
With the above teaching, the following verse from the Torah (Vayikra: 13; 45) will be understood: “And 'impure, impure' he shall call out.” Our Rabbis of Blessed Memory have explained that [the one afflicted with tzara’as] must make his [troublesome situation] known to the masses [in order that] the masses will beseech [HaShem] to have mercy upon him. [The speaker of Lashon HaRa must appeal to the masses to pray to Hashem on his behalf], for [the Lashon HaRa that he spoke has led to] his prayer not being accepted Above, [in Heaven]. Therefore, the Torah revealed this [piece of] advice to us, [which is] specifically [meant for the benefit of] this troubled [individual, who is unable though his own prayers to successfully beseech HaShem to rid himself of his tzara’as affliction].
Furthermore, on account of this [sin of Lashon HaRa, the person's] holy soul departs from him, as is written earlier in this book in chapter three [where we quote from] the Holy Zohar (Parshas Tazria; Volume 3; 46b).
 Rechilus is talebearing.
 This teaching can be found in Chovos HaLevavos - "Duties of the Hearts": The Gate of Submission, chapter 7.
The following is from “Chovos HaLevavos”:
“A person should not strive to embarrass [the one who speaks Lashon HaRa] against him, he should not deny his words of [Lashon HaRa], nor should he shame [the speaker of Lashon HaRa] on account of revealing [that which was offensive] concerning him. Rather [the victim of the Lashon HaRa] should say to [the one who spoke Lashon HaRa against him]: ‘My brother, how [are my sins] which you noticed comparable to all of my sins about which you are unaware, which The Creator has kept hidden for so long. If my evil actions and sins were to be revealed to you, you would run from me and be fearful of the punishment that The Creator [will inflict upon you] on account of them. [This follows that which] one of the poets [wrote]: “If only my neighbors will smell my sins, they would then run away and distance themselves from my borders.” [Similarly], Iyov said, “Have I covered over my rebellious sins as do [other] people, [to conceal in my hidden place my sins which I have justified by my twisted logic?] (Iyov: 31; 33)
[However], if what was spoken against him was false, he should say to the speaker of [the Motzi Shem Ra]: “My brother, it is not surprising that The Creator has saved me [from committing] that which you accuse me of [committing] due to the abundance of good which he has bestowed upon me. Rather, that which is surprising to me is that He has kept hidden [sins] which are greater and more reprehensible from that which you have spoken [falsely] concerning me. Stop [your forbidden speech] and spare [yourself] your merits, [so] that you do not lose [those] merits, [though you are] unaware [of the subsequent loss of your merits]. For it is already related regarding one of the pious who [was the victim] of someone [speaking that which was] evil against him, that, once word arrived [that someone spoke that which is forbidden against him], he sent a basket full of the choicest [produce] of the land to the one who spoke against him. [The pious individual sent the following note along with the basket]: “[Word has] arrived to me that you sent a present [replete with some of] your merits, and, in exchange, I have paid you with this [basket].
Based on the above passage written by Rabbenu Bachya, zt”l, it is clear that one loses some or all of the merits they earned in exchange for speaking forbidden words against a fellow Jew.
 This teaching is found in the third volume of the Zohar (53a).
 The Zohar notes that a person is purified from their sin of Lashon HaRa once they "returned [from performing the sin through] repentance" and "accepted [that] repentance upon himself". Clearly there is a difference between "returned in repentance" and "accepted repentance upon himself". From the context of the Zohar, the first step is to "return in repentance", it being mentioned first and in the past tense, whereas "accepted repentance upon himself" is mentioned second, referring to that which he has already accepted upon himself to accomplish in the future.
Perhaps the difference between these two types of teshuvah (repentance) can be understood from the RaMBa"M in his section of the Mishneh Torah which details the laws of repentance (Hilchos Teshuvah, chapter 2)
Law 2: What is "Teshuvah"? That refers to when the sinner abandons his sin, removes [the sin] from his thoughts, and determines not to do that sin again, as it says, "An evildoer shall abandon his ways..." (Yeshayahu: 55; 7) [The sinner] should also regret his past [sinful actions], as it says, after I have returned [from my sins], I have regretted [having performed them]." The sinner must sincerely determine to never return to commit that sin and confess the sin that he has performed, as well as all that which he has taken upon himself.
Law 9: A person who sinned against his fellow is only forgiven once [that person] returns that which was taken from the victim, appeases him and asks his forgiveness for having wronged him. Once he has returned that which he has taken and been forgiven, then he is forgiven [for the sin that he has performed].
Based on the above, the repentance of the past seems to refer to the sinner (in our case, the speaker of Lashon HaRa), having accepted upon himself to not commit that sin in the future and regretting ever having committed that sin. The repentance which he has accepted upon himself for the future is described as fulfilling all that he has accepted upon himself as well as appeasing the person that he has wronged, in our case, by speaking Lashon HaRa. Once the sinner is forgiven by the victim, then he is completely forgiven. Hence, in order to become "pure" one must regret his past sinful actions, determine to never commit that sin again and accept upon himself to complete that action of repentance by asking the victim of his Lashon HaRa to forgive him, at that time he can become pure from his sin. However, that person only returns to his normal state of purity after living in the Israelite camp, outside of his tent for a period of a week. (Vayikra: 14) During that week he has time to ask forgiveness from those whom he had wronged. By the time the eighth day rolls around and the one who has spoken Lashon HaRa has completed his process of purification, he also has probably asked for and received forgiveness from the victim of his Lashon HaRa. For more on this, please see the "Twenty-Eighth Day".