Albert Barnes on Hebrews 3:10

Wherefore I was grieved. On the word grieved, Eph 4:30. The word here means that he was offended with, or that he was indignant at them.

They do alway err in their heart. Their long trial of forty years had been sufficient to show that it was a characteristic of the people that they were disposed to wander from God. Forty years are enough to show what the character is. They had seen his works; they had been called to obey him; they had received his law; and yet their conduct, during that time, had shown that they were not disposed to obey him. So of an individual. A man who has lived in sin forty years; who during all that time has rebelled against God, and disregarded all his appeals; who has lived for himself, and not for his Maker, has shown what his character is. Longer time is unnecessary; and if God should then cut him down, and consign him to hell, he could not be blamed for doing it. A man who during forty years will live in sin, and resist all the appeals of God, shows what is in his heart; and no injustice is done if then he is summoned before God, and he swears that he shall not enter into his rest.

And they have not known my ways. They have been rebellious. They have not been acquainted with the true God; or they have not approved my doings. The word know is often used, in the Scriptures, in the sense of approving, or loving. Mt 7:23.