1 Thessalonians 5:23
And the God of peace Himself sanctify you wholly, and may your spirit and soul and body be preserved complete, without blame, at the coming of our Lord Jesus Christ.
Some passages to which we will refer are very familiar. First Thessalonians 5:23 is a verse indicating that we are tripartite, or of three parts: the spirit, the soul, and the body.
For the word of God is living and operative and sharper than any two-edged sword, and piercing even to the dividing of soul and spirit and of joints and marrow, and able to discern the thoughts and intentions of the heart.
Hebrews 4:12 also mentions the spirit and the soul and the dividing of these two parts. If we would know Christ and enter into Him as the good land and as the rest, we must discern the spirit from the soul. The spirit is the very place where Christ dwells in us, so if we would know Christ in an experiential way, we must discern our human spirit from our soul. This verse mentions the difference not only between the spirit and the soul but also between the joints and the marrow of the body and between the thoughts and the intentions of the heart. The living word of God is a discerner of all these things. This proves that if we are going to know the Lord in a practical and real way, we must discern all these parts. What are the thoughts of the heart and the intentions of the heart? And how many parts are in the heart?
And Mary said, My soul magnifies the Lord, And my spirit has exulted in God my Savior;
In Luke 1:46-47 the soul and the spirit are again distinguished.
Philippians 1:27 says that we must stand firm in one spirit—not the Holy Spirit but the human spirit—and strive together with one soul. Again, this verse shows that there is a difference between the spirit and the soul.
Finally, Mark 12:30 says, “You shall love the Lord your God from your whole heart and from your whole soul and from your whole mind and from your whole strength.” Here are four different parts: the heart, the soul, the mind, and the strength. If we put all these verses together we will realize that there are quite a number of different parts within us besides the many parts of the body.
First Thessalonians 5:23 indicates that we are spirit, soul, and body, and Psalm 51 reveals the inward parts with the hidden part. The inward parts are the parts of the soul, which is proved by comparing Hebrews 8:10 with Jeremiah 31:33, where their mind is quoted as a variation of their inward parts. Just as the inward parts must be the parts of the soul, so the hidden part must be the spirit. Of all our parts, the spirit is the most hidden one within us. This inmost part is not only hidden within the body but is even hidden within the soul. Hence, there are the outward parts of the body, the inward parts of the soul, and the hidden part of the spirit.
(Excerpt from The Economy of God, ch. 6)