Alexander made another search for what to request of God, and found in Gospel that the disciples appointed to proclaim the kingdom of our lord Jesus Christ had numbered seventy. And he asked of God that this same number of faithful zealots, capable of broadcasting the word of God to the heathen Gentiles, be appointed from his own disciples. And this too God gave him, appointing out of Alexander's disciples seventy who were powerful in faith just as the holy man had asked.
I will tell the true story of how this came about. When his eight squadrons, arrayed in perfect faith, had with joy and gladness in their hearts been sending prayers and hymns up to God for quite some time, Alexander thought to himself and said, "Let no complacency infect this mighty suspension of earthly cares." And he returned to imposing harsh asperities upon his person, as was his way. And he convened a hundred and fifty noble soldiers of Christ who were truly armored with the breastplate of faith, the helmet of salvation and the sword of the Holy Spirit. He called each of them by name and said, "Brothers, let us test ourselves and the perfection of our faith. Let us cross that fearsome desert of the faithless, and show through our works that we believe in God with all our hearts, and not just in His word."
The original plan was to go to Egypt, and school the faithless of that place whose trust was in [the idols of] their own handwork. And his true disciples committed wholeheartedly to following him as soon as they heard the plan. But the Holy Spirit prevented this venture, and the blessed Alexander resolved to quit the monastery without telling anyone. "I am going to look in on our brothers in the desert," he told them instead, and assigned one Trophimus, a calm and gentle holy man of God, to be their abbot. And with his usual exhortations and a prayer, he bid them all farewell and left. And then he took back off across the Euphrates River.
From The Life of Alexander the Sleepless III.31-2