something handed over as a guarantee: security put up to back a promise, or a token brought back as proof
This word comes out of the world of ancient borrowing and lending. When a person could not be trusted to pay on his own, someone else stepped in and made himself answerable for the debt, and something changed hands to seal it: a handshake, an object, a written note. This noun names that guarantee, the thing that turns a bare promise into something a person can actually collect on.
A guarantee can be either the exposure you take on or the object you hand over, and the word covers both ends of it. In Proverbs it is the risk a foolish man accepts for a neighbor's debt, the ancient equivalent of co-signing a loan. In 1 Samuel it is something concrete that David is sent to bring home from the battle line, evidence that his brothers are still alive. The core idea is the same in both places: a guarantee that makes a claim good.
The words around it fill in the picture. The verb עָרַב is the act of standing good for someone else, עֵרָבוֹן is the deposit a debtor hands over and gets back once he pays, as Judah leaves his seal, cord, and staff with Tamar in Genesis 38, and תַּעֲרֻבָה names captives held as a living guarantee of a defeated people's good behavior. Centuries later the same commercial idea reached Greek as ἀρραβών, the down payment that secures the whole sum, which Paul uses for the Spirit as God's guarantee of everything still promised.
Nuances
What David is instructed to take in 1 Samuel 17:18: a concrete pledge or token of his brothers' welfare, a documentary receipt, or an oral report of how they are.
- majorityA concrete token or pledge brought back as proof that the brothers are alive and well, since the phrase stands immediately beside the instruction to see to their welfare.; BDB, s.v. עֲרֻבָּה (following Thenius and S. R. Driver): "a token from them, i.e. response, token of welfare"; C. F. Keil and F. Delitzsch, Biblical Commentary on the Books of Samuel (Edinburgh: T. & T. Clark)
- minorityA report or confirmation of the brothers' welfare rather than any physical pledge.; David Toshio Tsumura, The First Book of Samuel, NICOT (Grand Rapids: Eerdmans, 2007)
- minorityThe phrase cannot be pressed for a precise sense, because 1 Samuel 17:12 to 31 is a Masoretic expansion absent from the Old Greek of Codex Vaticanus, so no early Greek witness renders the word here.; P. Kyle McCarter, I Samuel, Anchor Bible 8 (Garden City, NY: Doubleday, 1980), 301-306; Emanuel Tov, "The Composition of 1 Samuel 16-18 in the Light of the Septuagint," in The Greek and Hebrew Bible (Leiden: Brill, 1999), 333-362