He was the only son of Katarzyna and Tomasz Stasievich, deeply religious Orthodox peasant parents living in Tarnogród.

As the future clergyman recalled, during his childhood, pilgrims often stayed overnight at their home, telling him about the shrines they visited and the saints honored there.

[1] Despite becoming the sole breadwinner of the family at this point, his mother agreed to him abandoning his job to pursue studies at the Orthodox Theological Seminary in Chełm, so that he could become a priest.

[3] His time at the monastery in Jabłeczna played a significant role in the life of the future saint, who always considered its patron, St. Onuphrius, his special protector.

[1] In 1915, together with all the monks, he fled from the advancing front lines to Moscow, where he initially stayed temporarily and in 1916 was accepted permanently into the Epiphany Monastery.

The Epiphany Monastery was by then registered as a labor commune to avoid being shut down, with Hegumen Leontius serving as the chairman of the residents' committee.

He worked to improve the financial situation of the declining monastery,[5] as well as to restore order in the monastic life, including the proper scheduling of services according to the rule.

[2] The accused were specifically charged with organizing a group of "fanatical women", including former nuns, who were involved in collecting money for the exiled Bishop Gregory and caused "excesses" when the Suzdal Cathedral was closed.

Archimandrite Leontius was also accused of using quotes from the Holy Scriptures to argue for the imminent fall of the Soviet Union.

The clergyman did not confess to the charges[2] and was sentenced to three years in a labor camp in the Komi Republic, where he worked as a medic assisting a brigade of prisoners building a road.

However, after a year of ministry, he was arrested again, accused of conducting religious agitation among children, opposing collectivization, and participating in a secret monarchist organization.

[5] The clergyman admitted only to giving small gifts (pens and pencils) to children, as he claimed he did not want them to engage in hooligan behavior.

[6] Archimandrite led an ascetic lifestyle, performing all the services held in the monasteries, teaching youth, and calling on parishioners to refrain from work on holidays.

This time, he was charged with spreading anti-Soviet content in his sermons, particularly by prophesying the imminent end of the world and interpreting the Holy Scriptures in an anti-state manner.

[6] On 20 July 1955, Bishop Benedict of Ivanovo assigned Archimandrite Leontius to the parish of Saint Michael the Archangel in Mikhaylovskoye.

[6] In recognition of his success in pastoral work, in 1960 he was appointed by Bishop Hilarion to the diocesan council and made the confessor for the clergy of the diocese.

In the same year, the Patriarch of Moscow and all Russia honored the clergyman with the right to celebrate the Holy Liturgy with the royal doors open during the Cherubikon.

[6] In 1963, due to numerous requests from the parishioners of Mikhaylovskoye, the new Bishop of Ivanovo, Leonid, sent the Archimandrite back to this town.

The following day, he suddenly fell ill and passed away on 9 February in the parish house, surrounded by the church choir, which sang liturgical hymns for him.

The following year, the Council of Bishops of the Moscow Patriarchate included him among the New Martyrs and Confessors of the Russian Orthodox Church,[7] granting him the title of The Venerable.