Cyril of Alexandria

The rich man who has despised many things will naturally expect a reward, but he who possessing little resigns what he has, may fairly ask what there is in store for him; as it follows, Then Peter said, Lo, we have left all. Matthew adds, What shall we have therefore? (Matt. …

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

At this, Peter asks: "behold, we have left everything," and he asks not for himself alone, but for the consolation of all the poor. Lest only the rich have good hopes of receiving much, as those who renounced much, while the poor have no hope, as those who renounced little and therefore earned a small reward — for this reason Peter asks and hears in response that both in the present and the future age, everyone who has despised his possessions for God's sake will receive recompense, even if those possessions were small. …

Commentary on Luke ↗

Bede

But Peter said: Behold, we have left everything and followed you. Great confidence. Peter was a fisherman, he was not rich, he sought food by hand and skill, and yet he speaks confidently, We have left everything. And because it is not enough to just leave, he adds what is perfect: And followed you. We have done what you commanded, so what reward will you give us?

On the Gospel of Luke ↗

Bonaventure

But Peter said. After he commended poverty through its perfection in merit and through its imperfection in the contrary, here thirdly he shows it commendable on account of its consummation in reward. Concerning the description of this, the procedure follows this order. For here the loftiness of perfect poverty is introduced as authoritative through apostolic observance, as approved through divine judgment, as enriched through grace, as rewarding through glory. …

Commentary on Luke, Chapter 18 ↗