John Moschos: greater love has no man than this

 When the Maziques¹ came and overan all that region, they came to [the Great] Oasis and slew many monks, while many others were taken prisoner. Among those taken prisoner at the Lavra were Abba John, formerly lector at the Great Church in Constantinople, Abba Eustatios the Roman, and Abba Theodore, all three of whom were sick. When they have been captured, Abba John said to the barbarians: "Take me to the city and I will have the bishop give you twenty four pieces of gold". So one of the barbarians led him off and brought him near to the city. Abba John went in to the bishop. Abba Leo was in the city at that time and so were some others of the fathers, that is why they were not captured. Abba John went in and began to implore the bishop to give the barbarian twenty four pieces of gold, but the bishop could only find eight. He was willing to give these to the barbarian, but he would not take them. "Either give me twenty four pieces of gold or the monk", he said. The men of the fortress had no choice but to hand over Abba John (who wept and groaned) to the barbarian; they took him away to their tents. Three days later, Abba Leo took the eight pieces of gold and went out into the wilderness to where the barbarians were camped. He pleaded with them in these words: "Take me and these eight pieces of gold, and let those [three monks] go. For, as they are sick and cannot work for you, you will have to kill them. But as for me, I am in good health and I can work for you". Then the barbarians took both him and the eight pieces of gold of which he spoke, letting the other three [monks] go free. Abba Leo went off somewhere with them and when he was exhausted [and could go no further], they beheaded him. And Abba Leo fulfilled that which is spoken in the scriptures: "Greater love hath no man that this, that a man lay down his life for his friends (John 15:13). Then we knew what he was talking about when he used to say: "I am going to reign", for reign he did, having laid down his life for his friends.
+John Moschos, from The Spiritual Meadow, #112. The Life and Death of Leo, a Cappadocian Monk
¹ Barbarian invaders from Mauretania.