Rav Yaakov Yosef of Ostrog testified that he heard from the Maggid of Mezritch about the Ramchal that, “His generation did not understand him or appreciate his great righteousness.” (Printer’s Introduction to Kelach Pischei Chochmah Koretz)
The Rav Simcha Zisel, the Alter of Kelm testified that the Vilna Gaon said: “I saw a great light descend to this world in the form of the sefer, Mesilas Yesharim.”
In his introduction to the Mesilas Yesharim, the Mahari Maltson wrote that when the sefer first came out, the Vilna Gaon said: “A new light had come into the world. If the Ramchal was still alive, I would walk on foot to see him and meet him face to face.” He wrote further that the GR”A reviewed the sefer often. When the Gaon received the Ramchal’s sefer, Adir BaMarom, a commentary on the Rashbi’s Idra Rabbah, he dressed in Yom Tov clothes to celebrate.
It is known that the GR”A said if he had been in the Ramchal’s generation he would have walked 12 milin to meet him. Also, it was known that the Kohznitzer Maggid studied Mesilas Yesharim as a prerequisite to any effort to ascend spiritual levels. (Rav Michel Yehuda Lefkowitz in his haskama to Mesilas Yesharim Mevuar)
The Kohznizter Maggid once said that any of the lofty spiritual levels that he himself attained were all thanks to the sefer, Mesilas Yesharim. (Dor Deah)
There is a tradition that the Apta Rav, author of Ohev Yisroel, said that his entire spiritual direction in life and his primary chinuch (education) came first and foremost from Mesilas Yesharim (Mesilas Yesharim HaMevuar Yakrus v’Chavivus Toras Ramchal p. 13)
I received a tradition from my holy forefathers that the mother of the heilige Ropshitzer commanded him in his youth to study Mesilas Yesharim, and he did so all the days of his life. He testified regarding himself that “mein mahus is Mesilas Yesharim – My entire being is Mesilas Yesharim.” (kisvei Rav Chacham Tzvi Halberstam)
Rav Moshe Teitelbaum, author of Yismach Moshe, testified: “I received a tradition from the Mezritcher Maggid in the names of Rav Yosef of Mezritch and Rav Pinchos Koretzer that the sefer, Kelach Pischei Chocmah is bahir v’tahor – luminous and pure!” (Avkas Rochel Moadim p. 91)
When Rav Shlomo Halberstam of Bobov taught his talmidim in his yeshivah in Vishnitza, he opened each shiur with a study in Mesilas Yesharim and other mussar seforim. (Kerem haChassidus vol. 2)
The Vizhnitzer Rebbe shlit”a, Rav Yisrael Hager writes in his haskama to Mesilas Yesharim haMevuar that the sefer, Mesilas Yesharim was known to Rav Chaim Meir, the Imrei Chaim, by heart and that his own father, Rav Moshe the Yeshuos Moshe of Vizhnitz, compelled the yeshiva students to study it as part of their daily mussar regimen.
The rebbe of Pinsk-Karlin recalled how in his youth, one Elul, he and several other yungeleit came before Rav Moshe Mordechai of Lelov and asked him which sefer they should study to prepare themselves during Elul towards the approaching days of selichos and the Yomim Noraim? He thought for a few minutes and answered them: “During these days, it would be proper for you to study Mesilas Yesharim every day for about ten minutes before you eat.” (From his haskama to Mesilas Yesharim Mevuar)
I remember in my youth how I once entered the inner sanctum of the Imrei Chaim of Vizhnitz and I asked him which mussar sefer I should study on a constant basis. He answered me immediately: “Mesilas Yesharim is what you should study and attach yourself to, and then vesti zany a erlicher yid – then you can become an erlicher, pious Jew.” (Rav Naphtali Moskowitz, the Meilitzer of Ashdod, in his haskama to Mesilas Yesharim Mevuar)
I saw how my father [the previous Pittsburger Rebbe] was especially fond of the sefer, Mesilas Yesharim. From the day he set his mind to it, the holy sefer never left his hands. He himself testified to me that in his youth he had memorized it by heart and I saw how until his last days on this earth, he studied it intensely and added his own comments and ideas as he reviewed it. He had the custom to purchase a brand-new copy each time he completed the sefer. In the new copy, he would enter further comments and novel insights for himself--all this in order to increase his enthusiasm as if it was the very first time he had even studied the sefer. Happy are the eyes that saw this! (Pittsburger Rebbe zt’l of Ashdod in his haskama to Mesilas Yesharim Mevuar)
It is said in the name of the founder of the Mussar Movement himself, Rav Yisrael Salanter, that he used to say, “It is easier to author the entire Shas-- the whole Talmud-- than to write even just one chapter of Mesilas Yesharim.’ (Mesilas Yesharim HaMevuar Yakrus v’Chavivus Toras Ramchal)
Rav Yosef Weinstock, the mekubal, had a custom to study Mesilas Yesharim every day. When his daughter passed away from illness on Yom Kippur, he was supposed to sit shiva until the 14th of Tishrei (Sukkos), but his pain at giving up his daily Mesilas Yesharim shiur was so intense that he asked and received permission from the Minchas Yitzchok to continue his the shiur as usual! (Mesilas Yesharim HaMevuar Yakrus v’Chavivus Toras Ramchal)
The Ramchal also authored Tehillim--see: www.HebrewBooks.org/56107 --as well as a daily regimen of pesukim on trust in Hashem and hope for the ultimate redemption. The latter was built on six foundations: Trust, Hope, Wish, Unity, Love, and Truth. See: Pesukei Kivui L’Ramchal www.HebrewBooks.org/56107 and another version here: https://ramhal.net/doc/Pesuka-Kivuy.pdf
