Mark 8:36 For what shall it profit a man, if he shall gain the whole world, and lose his own soul?
John Bunyan "The Greatness of the Soul" adapted in Voices From The Past
http://www.bunyanministries.org/works/vol1/04_greatness_of_soul.pdf
The body is called the house of the soul. Now the house is much inferior to him that dwells in it. And yet, alas, with grief, how common it is for men to spend all their time, care, strength, and attention for the honour and preferment of the body, as if the soul were a poor, pitiful, and sorry thing, not worthy of thinking about, or caring for! Yet, it is the body that our foolish fancies are taken with, and not that great noble part - the soul. The greatness of the soul is manifest by the greatness of the price paid for it to make it an heir of glory: His precious blood (1 Peter 1:18-19).
We esteem things according to the price paid for them. The soul has been purchased by a price that the Son and wisdom of God thought appropriate to pay for its redemption. (1 Corinthians 6:20). Christ sat on the throne of heaven and looked at the souls of men trampled under the law and under the penalty of death. What did he do? He came down from his throne, stooped down to earth, and there he laid down his life and blood for them (2 Corinthians 8:9). Would he have done this for inconsiderable things? No, nor would he for the souls of sinners either, if he had not valued them higher than he valued heaven and earth besides.
O what great things are the souls of the sons of men! God sought the souls of man for companionship, and the soul is capable of communion with him when the darkness of sin is removed. The soul has intelligent power, and it can know and understand depths, heights, lengths, and breadths, in those high, sublime, and spiritual mysteries that only God can reveal and teach (Daniel 2:28); yea, it is is capable of diving unutterably into them. God has made the creature capable of hearing, knowing, and understanding his mind when opened and revealed to it (1 Corinthians 2:10).
John Newton, ‘Letter to a Nobleman’ (William Legge, Earl of Dartmouth), in "Cardiphonia", in Works of John Newton
Should I suggest in some companies, that the conversion of a hundred sinners to God is an event of more real importance than the temporal prosperity of the greatest nation upon earth, I should be charged with ignorance and arrogance; but your Lordship is skilled in Scriptural arithmetic, which alone can teach us to estimate the value of souls, and will agree with me, that one soul is worth more than the whole world, on account of its redemption price, its vast capacities, and its duration.
Thomas Brooks "An Ark For All God's Noahs"
The soul is the beauty of man, the wonder of angels, and the envy of devils. Nothing can satisfy the soul without God. He is a portion that is exactly suited to the condition of the soul in its desires, needs, wants, longings and prayers. (In Him) is light to enlighten the soul, wisdom to counsel the soul, power to support the soul, goodness to supply the soul, mercy to pardon the soul, beauty to delight the soul, glory to ravish the soul, an fullness to fill the soul.
John Flavel "The Love of God in Giving His Own Son for Us"
Learn hence the exceeding preciousness of souls, and at what a high rate God values them, that he gave his Son, his only Son out of his bosom, as a ransom for them. Surely this speaks their preciousness: all the world could not redeem them; gold and -silver could not be their ransom; so speaks the apostle, ‘You were not redeemed with corruptible things, as silver and gold, but with the precious blood of Christ.’ (1 Peter 1:18) Such an esteem God had for them, that rather than they should perish, Jesus Christ shall be made a man, yea, a curse for them. Oh, then, learn to put a due value upon your own souls: do not sell that cheap for which God hath paid so dear: remember what a treasure you carry about you; the glory that you see in this world is not equivalent in worth to it. ‘What shall a man give in exchange for his soul?’ (Matthew 16:26)
George Swinnock The Christian Man's Calling
Soul-work is weighty work and not to be trifled with. It is the business of every man. One soul is worth ten thousand worlds. The body came from dust, but the soul from the breath of God.
Ezekiel Hopkins The Vanity of the World
http://www.puritanboard.com/f29/works-ezekiel-hopkins-23189/
We should be soaring aloft with God on wings of meditation and affection, and here we are grovelling in the clay and muck of this world. Do we not degrade ourselves, when we stoop to admire what is so vastly below us, and barter away our precious souls? Our souls are worth more than ten thousand worlds and yet we seek to gain a small part of this one. What folly it is to purchase a vain world at the loss of our precious souls!
The Serampore Form of Agreement (William Carey)
https://www.desiringgod.org/articles/may-our-hearts-bleed
Article 1
In order to be prepared for our great and solemn work, it is absolutely necessary that we set an infinite value upon immortal souls; that we often endeavor to affect our minds with the dreadful loss sustained by an unconverted soul launched into eternity. . .If we have not this awful sense of the value of souls, it is impossible that we can feel aright in any other part of our work.
Article 4
Life is short . . . all around us are perishing, and . . . we incur a dreadful woe if we proclaim not the glad tidings of salvation. . . Oh! may our hearts bleed over these poor idolaters, and may their case lie with continued weight upon our minds.
J.C. Ryle Old Paths, Chapter 2 - "The Soul"