Isidore was an Egyptian by birth, the son of a prominent family, and the kinsman of the Alexandrian Patriarchs Theophilus and Cyril. Having studied all the secular disciplines, he renounced worldly riches and glory, and for the love of Christ he devoted himself completely to the spiritual life.
He was a great and ardent defender and interpreter of the Orthodox Faith. According to the historian Nicephorus, St. Isidore wrote more than ten thousand letters to various individuals. In these he reproached some, counseled others, and comforted and instructed still others.
In one letter St. Isidore wrote: “It is more important to teach by a life of doing good than to preach in eloquent terms.” In another, he said: “If one desires that his virtues appear great, let him consider them small, and they will surely manifest themselves as great.” The first and basic rule for St. Isidore was this: “First do and then teach, according to the example of our Lord Jesus.”
At the time of the persecution of St. John Chrysostom, when the entire population was divided into two camps–one for him and one against him–St. Isidore, this great pillar of Orthodoxy, sided with St. John Chrysostom. He wrote to Patriarch Theophilus that Chrysostom was a great light of the Church, and begged him to avoid rancor toward him. Isidore lived long and accomplished much, glorifying Christ God with his life and his writings. Isidore took up habitation in the Kingdom of Christ in about the year 436 A.D.
Apolytikion of Isidore of Pelusium
Plagal of the Fourth Tone
The image of God, was faithfully preserved in you, O Father. For you took up the Cross and followed Christ. By Your actions you taught us to look beyond the flesh for it passes, rather to be concerned about the soul which is immortal. Wherefore, O Holy Isidore, your soul rejoices with the angels.
Kontakion of Isidore of Pelusium
O All-Blessed Isidore, the Church hath found thee as another morning star; and with the lightning of thy words she is illumined and crieth out: Rejoice, O ven’rable Father of godly mind.
Source: oca.org / goarch.org