Charles H. Spurgeon on Psalms 95:8

Harden not your heart. —Heart is ascribed to reasonable creatures, to signify sometimes the whole soul, and sometimes the several faculties appertaining to the soul.

1. It is frequently put for the whole soul, and that for the most part when it is set alone; as where it is said, "Serve the Lord with all your heart", 1Sa 7:20.

2. For that principal part of the soul which is called the mind or understanding. "I gave my heart to know wisdom", Ec 1:17. In this respect darkness and blindness are attributed to the heart, Eph 6:18, Ro 1:21.

3. For the will: as when heart and soul are joined together, the two essential faculties of the soul are meant, namely, the mind and will: soul put for the mind, heart for the will "Serve the Lord with all your heart and with all your soul", De 6:13.

4. For the memory. "I have hid thy word in my heart", saith the prophet, Ps 119:11. The memory is that faculty wherein matters are laid up and hid.

5. For the conscience. It is said that "David's heart smote him", that is, his conscience, 1Sa 24:5 2Sa 24:10. Thus is heart taken, 1Jo 3:20-21.

6. For the affections: as where it is said, "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind", Mt 22:37. By the mind is meant the understanding faculty; by the soul, the will; by the heart, the affections.

Here in this text the heart is put for the whole soul, even for mind, will, and affections. For blindness of mind, stubbornness of will, and stupidity of affections go together. —William Gouge.