Rashi on Isaiah
stout-hearted You who have strengthened your heart among the heathens (the nations [Parshandatha, K’li Paz]) and have clung to Me.
Ibn Ezra on Isaiah
Stouthearted, that do not believe in the word of the Lord, but are hardened in their hearts.
Rashi on Isaiah
that are far from righteousness For it has been a long time for you, and I have not demonstrated to you My righteousness to redeem you.