The true means of acquiring Cleanliness is diligence in study of the words of our sages, of blessed memory, both in matters of Halacha (Jewish law) and in matters of mussar (ethics).
For after a person has truly understood the obligation of Cleanliness and its necessity, having already attained Watchfulness and Zeal by engaging in the means they are acquired and distancing from their detriments, behold, he will no longer have any more obstructions preventing him from attaining Cleanliness except knowledge of the fine details of the Mitzvot in order to guard himself in all of them.
Therefore, he necessarily must attain comprehensive knowledge of the Halachot to their full depth in order to know the extent of reach of the branches of the mitzvot.
Also, since one is prone to forgetfulness in these fine details, he will need diligent study in the books explaining these fine details to renew remembrance of them in his mind. Then certainly, he will be roused to fulfill them.
Likewise regarding the character traits, it is necessary for him to read the teachings of mussar, whether of the early or later sages. For very often, even after one has resolved to become among the meticulously Clean, he may possibly sin in details he never attained knowledge in.
For man is not born wise and cannot know everything. But by studying the matters, he will be awakened to what he did not know, and he will contemplate on what he did not grasp previously, even matters not found in the books themselves. For when his mind is awakened to the matter, it goes and observes it from all perspectives, and draws forth new understandings from the wellspring of truth.
However, the factors which cause loss of this trait are all those detriments to the trait of Watchfulness, in addition to lack of proficiency in knowledge of the laws and ethics (Mussarim) as I wrote above. Our sages already stated: "an ignorant man cannot be pious" (Avot 2:5). For one who does not know cannot possibly do. Likewise they taught "great is study in that it brings one to doing" (Kidushin 40b).
בְּדַרְכֵי קְנִיַּת הַנְּקִיּוּת
הִנֵּה הָאֶמְצָעִי הָאֲמִתִּי לִקְנוֹת הַנְּקִיּוּת, הוּא הַתְמָדַת הַקְּרִיאָה בְּדִבְרֵי חֲכָמִים זַ"ל, אִם בְּעִנְיְנֵי הַהֲלָכוֹת וְאִם בְּעִנְיְנֵי הַמּוּסָרִים.
The true means of acquiring Cleanliness is diligence in study of the words of our sages, of blessed memory, both in matters of Halacha (Jewish law) and in matters of mussar (ethics).
כִּי הִנֵּה אַחַר שֶׁכְּבָר הִתְאַמֵּת אֵצֶל הָאָדָם חוֹבַת הַנְּקִיּוּת וְהַצֹּרֶךְ בּוֹ, אַחַר שֶׁכְּבָר הִשִּׂיג הַזְּהִירוּת וְהַזְּרִיזוּת בְּמָה שֶׁנִּתְעַסֵּק בְּדַרְכֵי קְנִיָּתָם וְהִתְרַחֵק מִמַּפְסִידֵיהֶם, הִנֵּה לֹא יִשָּׁאֲרוּ לוֹ עַתָּה עִכּוּבִים לִקְנוֹת הַנְּקִיּוּת אֶלָּא יְדִיעַת הַדִּקְדּוּקִים אֲשֶׁר בַּמִּצְוֹת, כְּדֵי שֶׁיּוּכַל לְהִזָּהֵר בְּכֻלָּם.
For after a person has truly understood the obligation of Cleanliness and its necessity, having already attained Watchfulness and Zeal by engaging in the means they are acquired and distancing from their detriments, behold, he will no longer have any more obstructions preventing him from attaining Cleanliness except knowledge of the fine details of the Mitzvot in order to guard himself in all of them.
וְעַל כֵּן הִנֵּה צָרִיךְ לוֹ בְּהֶכְרֵחַ יְדִיעַת הַהֲלָכוֹת עַל בֻּרְיָם, לָדַעַת עַנְפֵי הַמִּצְוֹת עַד הֵיכָן הֵם מַגִּיעִים.
Therefore, he necessarily must attain comprehensive knowledge of the Halachot to their full depth in order to know the extent of reach of the branches of the mitzvot.
וְגַם לְפִי שֶׁהַשִּׁכְחָה מְצוּיָה בַּדְּבָרִים הַדַּקִּים הָאֵלֶּה, הִנֵּה תִּצְטָרֵךְ לוֹ הַתְמָדַת הַקְּרִיאָה בַּסְּפָרִים הַמְבָאֲרִים אֵלֶּה הַדִּקְדּוּקִים, לְמַעַן חַדֵּשׁ בְּשִׂכְלוֹ זְכִירָתָם, וְאָז וַדַּאי שֶׁיִּתְעוֹרֵר לְקַיְּמָם.
Also, since one is prone to forgetfulness in these fine details, he will need diligent study in the books explaining these fine details to renew remembrance of them in his mind. Then certainly, he will be roused to fulfill them.
וְכֵן בְּעִנְיַן הַמִּדּוֹת מֻכְרַחַת לוֹ קְרִיאַת מַאַמְרֵי הַמּוּסָר לַקַּדְמוֹנִים אוֹ לָאַחֲרוֹנִים. כִּי פְּעָמִים רַבּוֹת אֲפִלּוּ אַחַר שֶׁיִּקְבַּע הָאָדָם בְּעַצְמוֹ לִהְיוֹת מִן הַמְּדַקְדְּקִים הַנְּקִיִּים, אֶפְשָׁר לוֹ שֶׁיֶּאְשַׁם בִּפְרָטִים, מִפְּנֵי שֶׁלֹּא הִגִּיעָה יְדִיעָתוֹ בָּהֶם.
Likewise regarding the character traits, it is necessary for him to read the teachings of mussar, whether of the early or later sages. For very often, even after one has resolved to become among the meticulously Clean, he may possibly sin in details he never attained knowledge in.
כִּי אֵין אָדָם נוֹלַד חָכָם וְאִי אֶפְשָׁר לוֹ לָדַעַת אֶת הַכֹּל, אַךְ בִּקְרִיאַת הַדְּבָרִים יִתְעוֹרֵר בַּמֶּה שֶׁלֹּא יָדַע, וְיִתְבּוֹנֵן בַּמֶּה שֶׁלֹּא הִשְׂכִּיל מִתְּחִלָּה. וַאֲפִלּוּ בַּמֶּה שֶׁלֹּא יִמְצָא בַּסְּפָרִים עַצְמָם, כִּי בִּהְיוֹת שִׂכְלוֹ נֵעוֹר עַל הַדָּבָר, הוֹלֵךְ וּמַשְׁגִּיחַ הוּא עַל כָּל הַצְּדָדִין וּמַמְצִיא עִנְיָנִים חֲדָשִׁים מִמְּקוֹר הָאֱמֶת.
For man is not born wise and cannot know everything. But by studying the matters, he will be awakened to what he did not know, and he will contemplate on what he did not grasp previously, even matters not found in the books themselves. For when his mind is awakened to the matter, it goes and observes it from all perspectives, and draws forth new understandings from the wellspring of truth.
וְאָמְנָם מַפְסִידֵי הַמִּדָּה הַזֹּאת, הִנֵּה הֵם כָּל מַפְסִידֵי הַזְּהִירוּת, וְנוֹסַף עֲלֵיהֶם חֶסְרוֹן הַבְּקִיאוּת בִּידִיעַת הַדִּינִים אוֹ הַמּוּסָרִים, כְּמוֹ שֶׁכָּתַבְתִּי. וּכְבָר אָמְרוּ זַ"ל (אבות פרק ב): וְלֹא עַם הָאָרֶץ חָסִיד, כִּי מִי שֶׁלֹּא יָדַע, אִי אֶפְשָׁר לוֹ לַעֲשׂוֹת. וְכֵן אָמְרוּ (קדושין מ): תַּלְמוּד גָּדוֹל שֶׁמֵּבִיא לִידֵי מַעֲשֶׂה.
However, the factors which cause loss of this trait are all those detriments to the trait of Watchfulness, in addition to lack of proficiency in knowledge of the laws and ethics (Mussarim) as I wrote above. Our sages already stated: "an ignorant man cannot be pious" (Avot 2:5). For one who does not know cannot possibly do. Likewise they taught "great is study in that it brings one to doing" (Kidushin 40b).