Here are quotes from famous Kabbalists:
WITHOUT THE STUDY OF THE ZOHAR, THE PNIMIUT HA TORAH, THE REST OF OUR STUDY WILL BECOME A POTION OF DEATH, G-D FORBID
Behold [the expression] 'the Tree of Life' refers to Pnimiut HaTorah, the inner dimension of the Torah, as stated in [the passage from] the Raya Mehemna, Parshas Naso, [cited above]: 'Since in the future, the Jews will taste the Tree of Life which is the Sefer Ha Zohar, Tanya, Iggeres HaKodesh', explains that the term 'the Tree of Life' refers to 'the inner dimensions of the Torah and its mitzvos.'
To explain: The Written Law is referred to as 'the Tree of Life' because it does not enclothe itself in material garments to the same degree [as does the Oral Law]. (For [the Written Law emanates] from Zaer Anpin.) And in [the Written Law], G-dly light can be sensed.
Similarly, Pnimiyus HaTorah has not enclothed itself in material garments, for instead, it speaks of spiritual matters including the chainlike progression of spiritual existence and G-dly subjects. Moreover, the conceptualization and the comprehension of these matters is spiritual and in [this type of thought], the G-dly light can be felt.
Its entire intent is to know G-d and to come to love and fear Him, as the Shaloh writes in his Masechta Shavuos, p. 183b ,269 with regard to the study of Torah lishmah:
The words of Torah that involve research, knowledge, and comprehension [of G-d Himself should be studied in order to know His name and His greatness, and the hidden secrets of His mitzvos. Then the person's heart will be roused to fear Him and to love Him.
RABBI SHALOM DOV BER MI LUBAVITCH ZTK'L KUNTRES ETZ CHAYYIM
THE STUDY OF THE ZOHAR HA KADDOSH IN OUR TIMES IS VERY NECESSARY TO PROTECT AND SAVE US FROM ALL EVIL
The study of the Zohar ha Kaddosh in our times is very necessary to protect and save us from all evil. For the revelation of this wisdom in our times, helps to purify and protect us greatly so that we will be able to cling with a complete heart to our Father in Heaven.
For the people of prior generations were Tzaddikim and Chassidim and people of great deeds, and thus were saved from the accusers, but now we are far removed from our source, and what will protect us if not our reading this Wisdom?
Rabbi Yaakov Tzemach, Hakdama le Etz Chayim
ONE HOUR OF THE STUDY OF ZOHAR IS THE EQUIVALENT OF THIRTY DAYS OF THE STUDY OF THE PLAIN MEANING OF TORAH
Our Holy Master Rabbi Chayim Vital, may his merit shield us, in the introduction to the book Etz Chayim, warned the students of the Torah, those who listen to the Word of G-d, the great obligation they have to study the hidden Torah [Kabbalah], and the great punishment for neglecting its study, because one hour of this study does the same as thirty days of the study of Pshat (plain meaning of the Torah)
(Kise Melech on Tikune Zohar 30, 73b)
THEY CAUSE THE TORAH TO BE DESERTED BECAUSE THEY DO NOT OCCUPY THEMSELVES WITH THE WISDOM OF THE KABBALAH
"And all his kindness is like the grass of the field" (Yeshayahu 40:6) All the kindness that they do, they do only for themselves. And even all those that occupy themselves in the Torah, all the kindness that they do, they do for themselves...Woe to those who cause him [The Mashiach] to leave from the world and don't come, and they are those who cause the Torah to be deserted and do not wish to occupy themselves with the Wisdom of the Kabbalah, for they cause the spring of wisdom to depart which is the YUD, and the BEIT is left on its own (Dried up). Woe to those that they cause poverty, sword, death and destruction...
Tikkune Zohar Tikkun 30
chanoch adds: The Yud mentioned above is HaShem who conceals himself when the Kabbalah is not studied. The Beit mentioned above is referring to the Torah itself as the first letter is the Beit. This comment is to help you understand this section.
IT IS IMPORTANT TO STUDY THE ZOHAR HA KADDOSH
IN PUBLIC
"From the year 1540 onward, it is most important that all study the Kabbalah in public and preoccupy themselves with the study of Kabbalah. For through the merit of Kabbalah and in fact solely through Kabbalah will the Mashiach appear and forever efface war, destruction, social injustice, and above all, man's inhumanity".
Rabbi Avraham Azulai, Or ha Chama, Introduction
If the person does not occupy himself with the 4 levels of Torah study:
PESHAT REMEZ DERASH SOD [PARDES- Simple meaning, allusion, Homiletical level, and the secrets of the Torah] he is missing the Mitzvah of Talmud Torah which is great and is equivalent to all other Mitzvot in the Torah, and this person has to reincarnate until he will occupy himself with the four levels PARDES.
Kitve Ari ha Kaddosh, Shaar ha Mitzvot Alef
"It is a great obligation on all Israel to study the Zohar ha kaddosh every single day, even when it is said without understanding, for this builds worlds and he purifies and sanctifies his soul and there is no limit to the greatness of his reward because through this he brings redemption closer and brings great pleasure to His Creator . . Therefore everybody should at least study five pages per day of the Zahor ha Kaddosh.
Tzavaat Rav Meir Schwartz mi Faidhotz
"The Sefer ha Zohar is a Tikkun for the Baaal Teshuvah - The Man of Return to Hashshem."
"If he is meritorious to wake up before dawn. he should then study Sefer ha Zohar for in its merit the Jews will come out of Exile which resembles the night and even though he has not the merit to understand it, even so he shall learn the language for it purifies the soul".
Siddur Shaar ha Shamaim Seder Limud shel ha Kodmim
"And the main point is that when your soul will cling to the books that deal with Yirut Hashem, that you thereby will realize at every moment the great debt you owe to the Creator of all worlds, and in particular through the sefer ha Zohar which is the most important of all, and it will cause your heart to flare up in flames of fire, the Sefer ha Zohar is the key".
Sefer Sur me Rav ye Ase
"One should learn Sifre Kabbalah, and when he does not understand it he should learn the Zohar and the Tikkunim for they are a Segula to purify the Neshama"
Siddur ha Aziral of Rabbi Yaakob Kapil
"The study of the Sefer ha Zohar is more elevated than any other study, even if he does not know what he is saying and even if he makes mistakes. And it is a great Tikkun for the Neshama, because even though the Torah is composed of names of the Holy one Blessed be He, it is nevertheless clothed in many stories, and when the person reads, he understands the stories and puts his mind on the simple meaning of those stories, but the sefer ha Zohar has the secrets revealed, and the reader knows that there are secrets and the occult parts of the Torah, only that he does not understand because of the depth of the subject and the shortness of his understanding".
The Chida, More Ba Etzba Siman 44
"...And even when he is like an animal that does not know how to read, even with all this, his reward will be double and there is an insinuation in the verse (Tehillim) "Man and beast Hashem saves" where the Gematria of the words TOSHIA HASHEM (Saves Hashem) plus the letters plus the 2 words themselves equals the sum of the following: ZOHAR TIKKUNIM BE DIKDUK TZACH (TZADDI CHET - TZE CHASHOV) - chanoch adds: Zohar and the Tikunim is the grammer seed level of cleansing.
Hakdamat of the Editor of the Zohar edition printed in Livorno
chanoch's Commentary
You may have heard me say that when reading the Zohar in Hebrew or Aramaic that I do not understand - I realize that I made a mistake in pronunciation. When I go back and correct that mistake I make a Tikkun - a correction. This is because making a mistake is caused by our Tikkun which causes a blockage. When I go back and pronounce the words properly I make this correction and break that specific Klipah.
"He who studies the Zohar, even when he doesn't understand what comes out of his mouth, Ha Kaddosh Baruch Hu rectifies his words..."
Hakdamat of the Editor of the Zohar edition printed in Livorno
"It is necessary to read in the Sefer ha Zohar even when he does not know what it says, because it is a great correction to the Shechina and to his own soul as it is known for various reasons."
Tikkun Leil Shavuot Le ha Ramaz
"O that my people would listen to me, in this evil generation when heresy increases, It is proper to learn the Zohar and the Tikkunim with children nine years of age so that their fear of Hashem will precede their wisdom and will be maintained"
Notzer Chessed on Massechet Avot, Perek 4
"One who does not merit to understand The Zohar, he should nevertheless learn, because the language of the Zohar purifies the soul"
Ohr Tzaddikim by Rav Meir Papirash
"And we see that in regards to the study of the Mishna there are many opinions that say that one must understand what he is studying, but when reading Tehillim (Book of Psalms) or the Zohar even if one doesn't understand anything at all, it is important and received and desired by The Holy One Blessed Be He"
Pele Yoatz
"One who does not merit to understand The Zohar, he should nevertheless learn, because the language of the Zohar purifies the soul"
Ohr Tzaddikim by Rav Meir Papirash, a student of the Ari ha Kadosh
"Because of this work. the Book of the Zohar, [the Children of Israel] will be redeemed from exile"
The Zohar ha Kaddosh (3, 124b)
