If thou be surety for thy friend - לרעך lereacha, for thy neighbor; i.e., any person. If thou pledge thyself in behalf of another, thou takest the burden off him, and placest it on thine own shoulders; and when he knows he has got one to stand between him and the demands of law and justice, he will feel little responsibility; his spirit of exertion will become crippled, and listlessness as to the event will be the consequence. His own character will suffer little; his property nothing, for his friend bears all the burden: and perhaps the very person for whom he bore this burden treats him with neglect; and, lest the restoration of the pledge should be required, will avoid both the sight and presence of his friend. Give what thou canst; but, except in extreme cases, be surety for no man. Striking or shaking hands when the mouth had once made the promise, was considered as the ratification of the engagement; and thus the man became ensnared with the words of his mouth.
Surety - The “pledge,” or security for payment, which, for example, David was to bring back from his brothers 1 Samuel 17:18. So the word was used in the primitive trade transactions of the early Israelites.
In the warnings against this suretyship, in the Book of Proverbs, we may trace the influence of contact with the Phoenicians. The merchants of Tyre and Zidon seem to have discovered the value of credit as an element of wealth. A man might obtain goods, or escape the pressure of a creditor at an inconvenient season, or obtain a loan on more favorable terms, by finding security. To give such security might be one of the kindest offices which one friend could render to another. Side by side, however, with a legitimate system of credit there sprang up, as in later times, a fraudulent counterfeit. Phoenician or Jewish money-lenders (the “stranger”) were ready to make their loans to the spendthrift. He was equally ready to find a companion (the “friend”) who would become his surety. It was merely a form, just writing a few words, just “a clasping of the hands” (see the marginal reference) in token that the obligation was accepted, and that was all. It would be unfriendly to refuse. And yet, as the teacher warns his hearers, there might be, in that moment of careless weakness, the first link of a long chain of ignominy, galling, fretting, wearing, depriving life of all its peace. The Jewish law of debt, hard and stern like that of most ancient nations, aright be enforced against him in all its rigour. Money and land might go, the very bed under him might be seized, and his garment torn from his back Proverbs 20:16; Proverbs 22:27, the older and more lenient law Exodus 22:25-27 having apparently fallen into disuse. he might be brought into a life-long bondage, subject only to the possible relief of the year of jubilee, when the people were religious enough to remember and observe it. His wives, his sons, his daughters might be sharers in that slavery Nehemiah 5:3-5. It was doubtful whether he could claim the privilege which under Exodus 21:2 belonged to an Israelite slave that had been bought. Against such an evil, no warnings could be too frequent or to urgent.
Stricken thy hand - The natural symbol of the promise to keep a contract; in this case, to pay another man‘s debts. Compare Proverbs 17:18; Proverbs 22:26; Job 17:3; Ezekiel 17:18.