Ambrose of Milan

Let us also consider what recompense he requests from the Lord. He does not ask for riches, as would a greedy person, nor for a long life in this world, as would one who fears death, nor for power. Rather he asks for an heir worthy of his work. "What will you give me?"—he says—"I am about to depart without children." And then he says, "Because you have not given me posterity, a slave born in my house will be my heir." Let everyone learn therefore not to despise marriage. …

On Abraham ↗

Jerome

Lord God, what will you give me? And I go without children: and the son of my household, this Damascus Eliezer. And Abram said: Behold to me you have not given seed: and the son of my household will be my heir. Whereby we have, and the son of my household: in Hebrew it is written, Uben Mesech Bethi: which Aquila translated, the son of the one who gives drink to my house: that is, the son who gives drink to my house. But Theodotius, and the son of my servant: that is, his son, who is in charge of my house. …

Hebrew Questions on Genesis ↗

Bede

And Abram said: Lord God, what will you give me? I go childless, and the son of the steward of my house is this Damascus Eliezer. And Abram added: You have given me no offspring; and behold, my servant will be my heir. He does not ask as though doubtful of God's promises, but simply inquires what reward he, who has no son in whom to rejoice as heir and participant of the divine promise, will receive from the Lord, and whether his servant will be his heir instead. …

Commentary on Genesis (Hexaemeron) ↗