Theophylact of Ohrid

Thus they stood afar off, but were made nigh unto Him by their prayers. For the Lord is nigh unto all them that call upon him in truth. (Ps. 145:18.) Therefore it follows, And they lifted up their voices, and said, Jesus, Master, have mercy upon us. They do not merely supplicate or entreat Him as if He were a man, but they call Him Master or Lord, as if almost they looked upon Him as God.

Catena Aurea by Aquinas ↗

Titus of Bostra

They pronounce the name of Jesus, and gain to themselves the reality. For Jesus is by interpretation Saviour. They say, Have mercy upon us, because they were sensible of His power, and sought neither for gold and silver, but that their bodies might put on again a healthful appearance.

Catena Aurea by Aquinas ↗

Bede

Those who stood afar off, and lifted up their voice, saying: Jesus, Master, have mercy on us. And well, that they may be saved, they call Jesus Master. For indeed, in his words, they show they have erred, calling him the humble teacher of salvation, and when they return to the knowledge of the teacher, they immediately recur to the form of salvation. For it follows:

On the Gospel of Luke ↗

Bonaventure

And they lifted up their voice, expressing their misery: saying: Jesus, Master, have mercy on us, imploring divine mercy, according to that which the Prophet says in the Psalm: "I am afflicted and humbled exceedingly; I roared from the groaning of my heart." Spiritually, however, by the ten lepers is understood the universality of sinners sinning against the Decalogue; whence the Gloss: "Those who sin against the Decalogue, neither loving God, about whom they think wrongly, nor their neighbor, from whom they are divided, cry out to …

Commentary on Luke, Chapter 17 ↗