Mesilat Yesharim מסילת ישרים

Rabbi Moshe Chaim Luzzatto — the Ramchal — poet, kabbalist and thinker who lived in Italy and Amsterdam, built Mesilat Yesharim on a single baraita of Rabbi Pinchas ben Yair: study leads to watchfulness, watchfulness to alacrity, then cleanliness, separation, purity, piety, humility, fear of sin, and finally holiness.

The book takes each rung in turn: what it is, how to acquire it, what obstructs it. Its language is calm and almost legal, with no exaltation, and it opens by stating that the author writes not to teach anything new but to remind readers of what they already know — because that is precisely what gets forgotten.

The Vilna Gaon is said to have remarked that had the Ramchal been alive he would have walked to him to learn. It became the central text of the mussar movement.