Yahweh addresses Israel as the “house of Jacob” who is “named Israel” (Isaiah 48:1). They have Yahweh’s name in their mouths in oaths and commemorations (v. 1), but not in truth and righteousness. They have in fact become stiff-necked like the Hebrews who were brought from Egypt; they turn to their idols instead of Yahweh (v. 5).
They have become un-Jacob, a fact that is underlined in verse 4: “Your neck has an iron sinew (Heb. giyd ).” This alludes back to the Mosaic theme of “stiff-necked” Israel; it reaches further back to the story 0f Jacob’s wrestling with God, the very moment when Jacob was “named Israel.” Then, the Lord touched the sinew ( giyd ) and gave Jacob a permanent limp. Israel-of-the-iron-sinew, though, is impervious to Yahweh’s touch.
They don’t receive the healing wound; they don’t walk with the victorious limb. They are too stiff to bend to Him.