Monastic Foundation and Rule
Out of humility Euphrosynus declined to become igoumen of the community he had gathered, nominating instead his disciple Ignatius for the office. He compiled a monastic rule for the brotherhood, characterized in the sources as offering rather general advice for monks rather than detailed regulation.
His monastery became a seedbed for monasticism across the Pskov region. Among his disciples who themselves founded or led monasteries were Savva of Krypetsk, Dositheos of Verkhneostrov, Onouphrios of Malsk, Joachim of Opochsk, Hilarion of Gdovsk, and Chariton of Kudinsk.
The Alleluia Controversy
Euphrosynus is associated with a medieval Russian dispute over whether "Alleluia" should be sung twice or three times in liturgical prayer. He upheld the twofold practice against those, such as a priest named Job, who advocated singing it three times.
According to the tradition, he traveled to Constantinople in the 1420s to seek a resolution and received support for the twofold usage. The question remained contested in Russian practice for generations, and the threefold form eventually prevailed in the wider Church.
Testament and Legacy
His last testament is reported to survive on parchment, bearing the lead seal of Archbishop Theophilus of Novgorod, and is described as one of very few surviving wills written by a Russian ascetic in his own hand.
He is commemorated on May 15, the day of his repose, and traditionally also on the third Sunday after Pentecost among the saints of the Pskov region.