And when he saw that he prevailed not against him
That he, the man, or the Son of God in the form of man, prevailed not against Jacob, by casting him to the ground, or causing him to desist and leave off wrestling with him; not because he could not, but because he would not, being willing to encourage the faith of Jacob against future trials and exercises, and especially under his present one: besides, such were the promises that this divine Person knew were made to Jacob, and so strong was Jacob's faith at this time in pleading those promises in prayer to God, that he could not do otherwise, consistent with the purposes and promises of God, than suffer himself to be prevailed over by him: he touched the hollow of his thigh;
the hollow part of the thigh or the groin, or the hollow place in which the thigh bone moves, and is said to have the form of the hollow of a man's hand recurved: and the hollow of Jacob's thigh was out of joint, as he wrestled with
that is, the huckle bone, or the thigh bone, was moved out of the hollow place in which it was: this was done to let Jacob know that the person he wrestled with was superior to him, and could easily have overcome him, and obliged him to cease wrestling with him if he would; and that the victory he got over him was not by his own strength, but by divine assistance, and by the sufferance of the himself he wrestled with; so that he had nothing to boast of: and this shows the truth and reality of this conflict; that it was not visionary, but a real fact, as well as it teaches the weakness and infirmities of the saints, that attend them in their spiritual conflicts. The word used in this and the preceding verse comes from a root which signifies dust; it being usual with wrestlers to raise up the dust with their feet when they strive together, as Kimchi F7 remarks, as well as it was common with the ancients to wrestle in dust, and sand F8; and hence the phrase "descendere in arenam", combatants were called "arenarii".
F7 Sepher Shorash rad (qba) .
F8 "Fulva luctantur arena." --Virgil.