Adam Clarke on Hebrews 3:10

Wherefore I was grieved - God represents himself as the Father of this great Jewish family, for whose comfort and support he had made every necessary provision, and to whom he had given every proof of tenderness and fatherly affection; and because, they disobeyed him, and walked ill that way in which they could not but be miserable, therefore he represents himself as grieved and exceedingly displeased with them.

They do alway err in their hearts - Their affections are set on earthly things, and they do not acknowledge my ways to be right - holy, just, and good. They are radically evil; and they are evil, continually. They have every proof, of my power and goodness, and lay nothing to heart. They might have been saved, but they would not. God was grieved on this account. Now, can we suppose that it would have grieved him if, by a decree of his own, he had rendered their salvation impossible?