R. Jehiel was highly esteemed among the Hasidim and miraculous tales are related of his saintliness and asceticism, but he was strongly opposed by the Mitnaggedim. His distinctive spirituality is recalled by one of his disciples, who states that "it little mattered whether he had before him a Gemara or a kabbalistic text, for Jehiel saw in them only the means of serving God" (Likkutei Yekarim, 1872, 31b). In accordance with hasidic views, he considered the principle of devekut ("devotion" to God) to be of major importance and remarked that the way to attain this state was through the negation of reality (i.e., ecstasy). There are two roads to devekut. The positive way is to stand in fear and shame before the greatness of the Creator and hence through prayer, study, and good deeds to find the state of true love. Diligence in these practices will eventually lead to devekut. The negative way is through a denial of all physical desire. Jehiel Michael constantly preached on the need to uproot evil characteristics and destroy physical lusts. He knew that this way to devekut was difficult, for God had created man different from His own essence and therefore man could not maintain a constant state of devekut. Since the danger of his sinking into his physical nature was anticipated, God had imbued him with the will to achieve union with his source (i.e., God). Man's task is to conquer the material world and to view it not as the purpose of life but as a means of discovering that divinity which is reflected in the material and enlivens it. In this teaching, Jehiel Michael follows Dov Baer of Mezhirech, but he saw that this way was the most perilous for the ordinary man. He did not believe that constant devekut was possible for every man while he was engaged in physical activity, therefore he advised that physical acts should be preceded by meditation on the Divine Creator.

When preaching he would begin his sermons: "I do not only command and admonish you but myself as well..." (Or ha-Meir, on Zav). The true preacher, Jehiel believed, was the man who felt that he was merely a mouthpiece of the Shekhinah ("Divine Presence") and not a man who spoke in his own voice. His disciple attests that he "spoke at length and explained his statements several times" (Likkutei Yekarim, 28b). Jehiel Michael did not leave any writings of his own. Selections from his sermons were published in the anthology Likkutei Yekarim, as the sermons of "the Maggid Meisharim" of Yampol. Tradition attributes many sayings to him and stories about his wondrous deeds appear in various collections. Jehiel Michael was the founder of a dynasty of zaddikim which spread throughout Galicia and the Ukraine. He had five sons: Joseph of Yampol, Mordecai of Kremenets (teacher of Meir of Przemyslany and father-in-law of Aaron II of Karlin), Isaac of Radzivilov (author of Or Yizhak, 1961), Moses of Vladimir-Volnyski, and Ze'ev Wolf of Zbarazh.