Charles H. Spurgeon on Psalms 95:10

It is a people that do err in their heart. We may observe here, that he does not simply say, This people errs. What mortal is there that does not err? Or where is there a multitude of mortals, exposed to no errors? But he adds, "In their heart." Every error therefore is not blamed here, but the error of their heart is fastened upon. It is to be noted, therefore, that there is a twofold kind of error:

1. One is of the intellect, by which we go astray through ignorance. In this kind of erring Paul erred when he persecuted the Church of Christ; the Sadducees erred, not knowing the Scriptures, Mt 22:29; and to this day many in the Church go astray, endowed with zeal for God, but destitute of a true knowledge of Him.

2. The other kind of erring is of the heart and affections, by which men go astray, not through ignorance, but through corruption and perversity of heart. This error of heart is a mind averse to God, and alienated from the will and way of God, which is elsewhere thus described in the case of this very people: "And their heart was not right with Him." —Musculus.