This is an extract from a biography written by Bishop Leontios of Neapolis in the 7th century about the lives of Saint Symeon the Fool for Christ and Saint John. It's two paragraphs from Chapter 3, and it relates the story of when Saint Symeon left Saint John after they had spent 30 years together in the desert as hermits.
After they had spent twenty-nine years in the desert practicing every asceticism and mortification, in cold and in heat, enduring many and unutterable temptations from the Devil and conquering them, and had arrived at a high level (of virtue)—especially Symeon, who, because of his being innocent and very pure on account of the power of the Holy Spirit dwelling within him, perceived himself fearing neither suffering, nor cold, nor hunger, nor burning heat, but rather nearly exceeded the limit of human nature—he said to John, “What more benefit do we derive, brother, from passing time in this desert? But if you hear me, get up, let us depart; let us save others. For as we are, we do not benefit anyone except ourselves, and have not brought anyone else to salvation.” And he began to quote to him from the Holy Scripture such things as “Let no one seek his own good, but rather the good of his neighbor” [1 Cor 10:24], and again, “All things to all men, that I might save all” [1 Cor 9:22], and from the Gospel, “Let your light so shine before men, that they may see your good works and give glory to your Father who is in heaven” [Mt 5:16], and other such things. And lord John answered him, “I think, brother, that Satan is jealous of our silence and suggested this thought to you. On the contrary, sit down and let us complete our course in this desert, where we began and where we were called by God.” Symeon said to him, “Believe (me), I won’t stay, but I will go in the power of Christ; I will mock the world.” Again his brother said to him, “No, good brother, please, for the Lord’s sake, do not leave wretched me. For I have not yet reached this level, so that I can mock the world. Rather for the sake of Him who joined us, do not wish to be parted from your brother. You know that, after God, I have no one except you, my brother, but I renounced all and was bound to you, and now you wish to leave me in the desert, as in an open sea. Remember that day when we drew lots and went down to lord Nikon, that we agreed not to be separated from each other. Remember the fearful hour when we were clothed in the holy habit, and we two were as one soul, so that all were astonished at our love. Don’t forget the words of the great monk, with which he advised us on the night we left. Please don’t, lest I die and God demands an account of my soul from you.” Again Symeon said to him, “Think of me as dead. Wouldn’t you have to think about being alone by yourself? Believe me, if you come, it would be well and good, since I myself am not staying.” When brother John saw that he was persistent, he knew that he had been convinced by God to do this, since nothing would separate them except death, and perhaps not even that. For they had often prayed to God, that he would take the two of them together, and they knew that the Lord heard them in this as in all things.