When Avraham tasks his servant with traveling “to my land, to my birthplace” (Bereishit 24:4) to find a wife for Yitzchak, the servant expresses a fairly reasonable concern about what might go wrong – “Maybe the woman won’t want to follow me back here” (ibid. 5) – and wants to clarify backup plans in advance – “Should I return your son to the land from which you came [to marry her there]?”
Avraham, however, asserts that there is nothing to worry about: Definitely do not bring Yitzchak there, but don’t worry, because “Hashem, the God of heaven, who took me from my father’s house and from the land of my birth, and who spoke to me and who swore to me saying: I will give this land to your offspring – He will send His malach before you and you will take a wife for my son from there” (ibid. 7).
Why not worry?
That’s quite a mouthful. Why doesn’t Avraham simply say “God will help”? What is the relevance of these particular details about God to this assurance of His help? And what is the meaning of this particular assurance; what will an angel (malach) do, and how does Avraham know?
Some suggest, to answer the last question first, that Avraham didn’t actually know. The Hebrew future tense carries a degree of inherent ambiguity: does it mean something will happen, or should happen – that one hopes it will happen? Is Avraham saying “God will send His angel,” or is he saying “May God send His angel with you!” The Bechor Shor, among others, cites both possibilities: it could be a prayer or a promise. Chizkuni also offers two suggestions, but rather than “promise,” he pits prayer against prophecy.
Logic over worrying
Perhaps, then, Avraham did know that God would help – because He told him He would. Or, perhaps he was simply as certain as if he had been told, certain enough to make a promise to his servant – because he himself had been promised. In this light, we can offer a partial answer to the earlier question: Why are the details of God and Avraham’s biography relevant here?
A number of commentaries suggest something along the lines of this: “God made a point of bringing me here and telling me this land would be for my offspring; it’s only logical that He will make sure that I actually have offspring in this land to inherit it! For that to happen, it makes sense that Yitzchak will stay here and be joined, here, by a woman who is a good match to bring the next generation into the land with him.”
Prayer, prophecy, and promise
Of course, that line of reasoning only holds for someone who has some pretty strong faith. In this reading, Avraham puts his full trust in God and His promises, as well as in his own understanding of them, to the point that he can confidently tell his servant no, it is not possible that Yitzchak will have to go anywhere to find a wife; I am sure that God will help you find the right woman, and the right woman will be willing to join him here, where his (their) promised future lies.
At this point, one might argue that the lines between prayer, promise, and prophecy are not so distinct. Avraham desires and asks for God’s help, but he is so deeply connected to God, after decades of wandering and questioning and guidance and growth, that he can also be absolutely certain that what he wants is what God wants, and what God will do – because it is all held within the prophetic communications he has received.