Who knoweth the spirit of man - I think the meaning of this important verse is well taken by the above able writer: -

The nobler part of man, 'tis true, survives

The frail corporeal frame: but who regards

The difference? Those who live like beasts, as such

Would die, and be no more, if their own fate

Depended on themselves. Who once reflects,

Amidst his revels, that the human soul,

Of origin celestial, mounts aloft,

While that of brutes to earth shall downward go?"

The word רוח ruach, which is used in this and the nineteenth verse, has two significations, breath and spirit. It signifies spirit, or an incorporeal substance, as distinguished from flesh, or a corporeal one, 1 Kings 22:21, 1 Kings 22:22, and Isaiah 31:3. And it signifies the spirit or soul of man, Psalm 31:6; Isaiah 57:16, and in this book, Ecclesiastes 12:7, and in many other places. In this book it is used also to signify the breath, spirit, or soul of a beast. While it was said in verse 19, they have all one breath, i.e., the man and the beast live the same kind of animal life; in this verse, a proper distinction is made between the רוח ruach, or soul of man, and the רוח ruach, or soul of the beast: the one goeth upwards, the other goeth downwards. The literal translation of these important words is this: "Who considereth the רוח ruach) immortal spirit of the sons of Adam, which ascendeth? it is from above; (היא למעלה hi lemalah); and the spirit or breath of the cattle which descendeth? it is downwards unto the earth," i.e., it tends to the earth only. This place gives no countenance to the materiality of the soul; and yet it is the strongest hold to which the cold and fruitless materialist can resort.

Solomon most evidently makes an essential difference between the human soul and that of brutes. Both have souls, but of different natures: the soul of man was made for God, and to God it shall return: God is its portion, and when a holy soul leaves the body, it goes to paradise. The soul of the beast was made to derive its happiness from this lower world. Brutes shall have a resurrection, and have an endless enjoyment in a new earth. The body of man shall arise, and join his soul that is already above; and both enjoy final blessedness in the fruition of God. That Solomon did not believe they had the same kind of spirit, and the same final lot, as some materialists and infidels say, is evident from Ecclesiastes 12:7 : "The spirit shall return unto God who gave it."

knoweth

Ecclesiastes 12:7 Then shall the dust return to the earth as it was: and the spirit shall return to God who gave it.

Luke 16:22,23 And it came to pass, that the beggar died, and was carried by the angels into Abraham's bosom: the rich man also died, and was buried...

John 14:3 And if I go and prepare a place for you, I will come again, and receive you to myself; that where I am, there you may be also.

Acts 1:25 That he may take part of this ministry and apostleship, from which Judas by transgression fell, that he might go to his own place.

2 Corinthians 5:1,8 For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, an house not made with hands...

Philippians 1:23 For I am in a strait between two, having a desire to depart, and to be with Christ; which is far better:

of man that goeth upwards

But Thou who Both Hast Sons, and Livest in that End of the World...
11. But thou who both hast sons, and livest in that end of the world, wherein now is the time not of casting stones, but of gathering; not of embracing, but of abstaining from embracing; [2244] when the Apostle cries out, "But this I say, brethren, the time is short; it remains, that both they who have wives be as not having;" [2245] assuredly if thou hadst sought a second marriage, it would have been no obedience of prophecy or law, no carnal desire even of family, but a mark of incontinence alone. …
St. Augustine—On the Good of Widowhood.

The Holy War,
MADE BY SHADDAI UPON DIABOLUS, FOR THE REGAINING OF THE METROPOLIS OF THE WORLD; OR, THE LOSING AND TAKING AGAIN OF THE TOWN OF MANSOUL. THE AUTHOR OF 'THE PILGRIM'S PROGRESS.' 'I have used similitudes.'--Hosea 12:10. London: Printed for Dorman Newman, at the King's Arms in the Poultry; and Benjamin Alsop, at the Angel and Bible in the Poultry, 1682. ADVERTISEMENT BY THE EDITOR. Bunyan's account of the Holy War is indeed an extraordinary book, manifesting a degree of genius, research, and spiritual …
John Bunyan—The Works of John Bunyan Volumes 1-3

A Sermon on Isaiah xxvi. By John Knox.
[In the Prospectus of our Publication it was stated, that one discourse, at least, would be given in each number. A strict adherence to this arrangement, however, it is found, would exclude from our pages some of the most talented discourses of our early Divines; and it is therefore deemed expedient to depart from it as occasion may require. The following Sermon will occupy two numbers, and we hope, that from its intrinsic value, its historical interest, and the illustrious name of its author, it …
John Knox—The Pulpit Of The Reformation, Nos. 1, 2 and 3.