Deuteronomy 32:15

15. But Jeshurun waxed fat, and kicked--This is a poetical name for Israel. The metaphor here used is derived from a pampered animal, which, instead of being tame and gentle, becomes mischievous and vicious, in consequence of good living and kind treatment. So did the Israelites conduct themselves by their various acts of rebellion, murmuring, and idolatrous apostasy.

Robert Jamieson, A. R. Fausset & David Brown, 1871 · public domain

Verse 15 Jeshurun - ישרון the upright. This appellative is here put for Israel, and as it comes from ישר yashar, he was right, straight, may be intended to show that the people who once not only promised fair, but were really upright, walking in the paths of righteousness, should, in the time signified by the prophet, not only revolt from God, but actually fight against him; like a full fed horse, who not only will not bear the harness, but breaks away from his master, and endeavors to kick him as he struggles to get loose. All this is spoken prophetically, and is intended as a warning, that the evil might not take place. For were the transgression unavoidable, it must be the effect of some necessitating cause, which would destroy the turpitude of the action, as it referred to Israel; for if the evil were absolutely unavoidable, no blame could attach to the unfortunate agent, who could only consider himself the miserable instrument of a dire necessity. See a case in point, 1Sam 23:11-12 (note), where the prediction appears in the most absolute form, and yet the evil was prevented by the person receiving the prediction as a warning. The case is the following: - The Philistines attacked Keilah and robbed the threshing-floors; David, being informed of it, asked counsel of God whether he should go and relieve it; he is ordered to go, and is assured of success; he goes, routs the Philistines, and delivers Keilah. Saul, hearing that David was in Keilah, determines to besiege the place. David, finding that Saul meditated his destruction, asked counsel of the Lord, thus: "O Lord God of Israel, thy servant hath certainly heard that Saul seeketh to come to Keilah, to destroy the city for my sake. Will the men of Keilah deliver me up into his hand? Will Saul come down, as thy servant hath heard? And the Lord said, He will come down. Then said David, Will the men of Keilah deliver me and my men into the hand of Saul? And the Lord said, They will deliver thee up. Then David and his men (about six hundred) arose and departed out of Keilah, and went whithersoever they could go: and it was told Saul that David was escaped from Keilah, and he forbore to go forth." Here was the most positive prediction that Saul would come to Keilah, and that the men of Keilah would deliver David into his hands; yet neither of these events took place, because David departed from Keilah. But had he continued there, Saul would have come down, and the men of Keilah would have betrayed their deliverer. Thus the prediction was totally conditional; and so were all these prophecies relative to the apostasy of Israel. They were only fulfilled in those who did not receive them as warnings. See Jer 18:8-10. The Rock of his salvation - He ceased to depend on the fountain whence his salvation issued; and thinking highly of himself, he lightly esteemed his God; and having ceased to depend on him, his fall became inevitable. The figure is admirably well supported through the whole verse. We see, first, a miserable, lean steed, taken under the care and into the keeping of a master who provides him with an abundance of provender. We see, secondly, this horse waxing fat under this keeping. We see him, thirdly, breaking away from his master, leaving his rich pasturage, and running to the wilderness, unwilling to bear the yoke or harness, or to make any returns for his master's care and attention. We see, fourthly, whence this conduct proceeds - from a want of consciousness that his strength depends upon his master's care and keeping; and a lack of consideration that leanness and wretchedness must be the consequence of his leaving his master's service, and running off from his master's pasturage. How easy to apply all these points to the case of the Israelites! and how illustrative of their former and latter state! And how powerfully do they apply to the case of many called Christians, who, having increased in riches, forget that God from whose hand alone those mercies flowed!

Adam Clarke, 1831 · public domain

Here are two instances of the wickedness of Israel, each was apostacy from God. These people were called Jeshurun, "an upright people," so some; "a seeing people," so others: but they soon lost the reputation both of their knowledge and of their righteousness. They indulged their appetites, as if they had nothing to do but to make provision for the flesh to fulfil the lusts of it. Those who make a god of themselves, and a god of their bellies, in pride and wantonness, and cannot bear to be told of it, thereby forsake God, and show they esteem him lightly. There is but one way of a sinner's acceptance and sanctification, however different modes of irreligion, or false religion, may show that favourable regard for other ways, which is often miscalled candid. How mad are idolaters, who forsake the Rock of salvation, to run themselves upon the rock of perdition!

Matthew Henry, 1706 · public domain